In short go! You will have a wonderful time.
^This^
My wife & I went to Scotland & Ireland a few years ago, had a great time. Started out in the Borders region (Hadrians Wall), moved on to Edinburgh, then Stirling, Inverness, Culloden, Dornoch, etc till we ran out of time. We didn't rent a car, we bought Britrail passes and took the trains and buses.
http://www.britrail.net/passesWe made a list of places we wanted to see, took a Lonely Planet guidebook and headed off. Here are a few random thoughts:
Expect to be amazed, it is like no place I know of on this side of the Atlantic.
You don't need a tour, go on your own.
Travel light, we went two weeks on one bag each.
Figure on walking a lot, wear appropriate shoes.
People were very friendly and we almost speak the same language.
When in Edinburgh make sure to rub Greyfriars Bobby's head.
You must try Caledonian 80 shilling ale.
You must try haggis. You'll probably hate it, but you must try it.
You don't generally need reservations, there are B&B's everywhere. The exception would be during the really touristy times like Edinburgh's Festival in August.
If you go in summer, expect very long days, you are a lot further north than anywhere in the lower 48.
Expect to get rained on, expect it to be colder than NC.
Be ready to get off when the train stops (they don't stop for long).