The other day I realized that the early Ruger rimfire pistols were now C&R-able, so long story short, I found a nice seller on Gunbroker and a 1953-vintage Mk I is coming to me this week.

I'm totally new to these things, what should I know before I open the box?

Fushigi -"what should I know before i open the box" ? Easy - get to 'enjoy' the frustration you will feel when trying to RE-assemble the beast. Fitting the take down lever back into the upper receiver is a lesson in dexterity (and humility). You will learn to 'cus until such time as the planets align and the lever closes shut. Otherwise, look for the kits that eliminate all this and buy one...no more trips to the gunsmith with the parts in a paper bag LOL. I've a 5.5" HB Mk 1 and it's a dandy. Regards, Homesteader.

Go to the Ruger website and watch the videos. Buy Iowegans BOK. You can get them on
http://rugerforum.net/miscellaneous/26246-new-iowegan-gun-guides.html
These are really fun guns. They are not really that hard to take apart and put together. Watch the video on the Ruger website. It takes the mystery out of it. Get yourself a big paper clip to pull the backspring.
Buy a bunch of different 22 ammo and find the one it likes the best. Then load up on them. So far, mine likes a number of Winchester loads best. But I'm not that great of a shot, so maybe someone who is steadier and has good eye hand coordination would find something better.
I have not found a standard or high speed load that fails to function consistently. Never had a fail to feed or stove pipe. If it does, it probably needs cleaned and lubricated.
The only drawback is the bottom mag release. That takes a bit of getting used to.
Find a bunch of extra Ruger mags. I am not a fan of aftermarket mags in any of my rugers.
For me 22 mags are all a PIA to load, but I've got buggered up hands and the little things are hard for me to hold. A mag loader makes it a little easier.
I clean and lubricate mine every couple bricks of ammo.
Enjoy. Everybody ought to have one, they are just plain fun.
Bfly

No special issues that I'm aware of. Just shoot and enjoy.

Disassembly/reassembly isn't quite the nightmare you read on here, just make sure you have plenty of time when you do it for the first time.

I've had MK I, IIs, and now a III and out of all of them I wish I'd of kept the MK I.

Mags are easy to find for the MK I, I'd grab a couple extra. You'll get used to the bottom release and not pay much attention to it. Unless this is an IDPA trainer, you'll be happy with it.

They are good guns, and it'll take you a few times to figure out the re-assembly sequence, but it's not that hard.

The only thing I don't like is the magazine release, which is why I have a 22/45 mk II.

I've had mine since '78 and have put cases of ammo thru it. Clean it whenever it gets so cruddy the cycling slows.

It shot dime sized groups at 25 yards when new, now about 2.5 in.

Prolly difference between 19-year-old eyes and the rheumy orbs of a 51-year-old.

Does anyone know where custom grip panels for Mark I's can be bought?

Here's a link to a list of guys that make custom grips. I've been thinking of getting a set from woodpile. His look real nice. A lot of guys have given great comments on PrivateShultz's as well.
http://www.rugerforum.com/phpBB/viewtopic.php?t=95430&highlight=grip

Bfly

I got it last night--WOW! Its pretty substantial. Apparently its a pre-Mk I Standard since it lack the markings. Magazine has the knob on the right side and the grips are plain black synthetic. Condition is outstanding except for the frontstrap where it looked like someone wore a ring when shooting.

Mine came with the original instructions, I think I am going to try getting used to taking it apart.

Blackfly1 - can't agree with you more. Running ammo thru my Ruger is not the problem...it was the stigma of taking parts, in a bag, to the gunsmith to re-assemble it. Oh, the shame LOL! That was before Ruger produced the video's (Dxxmn good idea Ruger). Nowdays I use quality ammo, factory mags, spray cleaner and bucket so I DON'T have too. Be glad I'm not your brain surgeon! Regards, Homesteader.

Most if not all this stuff is on the MKII and MKIII but I gotta think it will apply to the MKI too.

http://guntalk-online.com/service.html

http://www.ar15.com/content/page.html?id=318

Well, I took it apart, it comes apart pretty easily, and its a rather straightforward design.

While still apart, I tried to put the mainspring housing back with the slide off so I could see how the parts are supposed to line up. Yeah, doing it blindly must be a pain.

No rust and very little wear BTW. I am curious about lubrication (how much and where) and if I should replace the recoil spring.

My paternal grand dad got me a Standard the day I was born. It's still shooting. My maternal Grand dad got me a Browning A5 Sweet Sixteen the same day. These are the firearms that got me started on this long and arduous journey. I still have both, and have had lots of fun over the years with them. The only thing that ever had to be replaced was the firing pin on the A5. I will leave them to one of my sons if we are still allowed to own such things in this country when I leave out of here.

Its still apart.

I decided to get a new recoil spring assembly, maybe it needs it, maybe not, but for under $10 from Brownells its cheap insurance.

Also picked out three additional vintage factory magazines from Gunbroker for about $27 each delivered. They are in better shape than the one that came with it!

I'm going to go light on the lubrication, it looks like it was designed to have very few critical friction points.

I've owned a half dozen of the earlier guns and Mk IIs, (I don't think they called the Standards Mark 'anythings' ), and the only part I've seen break on any of them was the recoil spring guide. One of the forks broke on the first gun I had. The pistol continued to function without a burp, too. Fine little guns. Shoot it, clean it, enjoy it, that's what they're made for.

Got it back together, it took all of five minutes and three tries.

I'll probably get some range time with it soon

the hardest part of take down for me was remembering whether it was suppose to cocked or fired at start. have to go look every time
as CRS. the answere is fired. don't buy a MK III, they ARE a PIA.