It really isn’t hard to do, especially if you are only replacing one. When making a rod from a bare blank care must be taken to keep the guides straight and on the correct side of the blank.
Is adhesive necessary? I'm guessing it's gonna be a very snug fit. The guide is fine, it's the insert alone that's broken. I've been reading and some claim they're ceramic, and others claim to be some type of alloy. I really don't care if it "matches" the rest, just need to replace the insert.
yes, you're going to want to put finish epoxy on the wraps after you replace the guide.
Guides come with a few different types of ring inserts. They can be ceramic, Sic, Hardaloy, and a couple more I'm not remembering right now.
mudhole.com is a good place to look to find replacement guides, and they even have a tutorial showing you how to do it.