I got the same keyboard in mint condition for $4, so first of all, I'd just like to gloat a little
I love this keyboard, and it's definitely worth restoring. It makes me sad when I read about people gutting them for parts.
I have yet to try it (on an Apple Extended II that I just bought) but if you search for 'retrobrite', you'll find lots of info about restoring yellowed plastic. The short version is to forget about all of the other chemicals and use the strongest peroxide you can find.
I picked up some 40 vol, which I believe is 12% from a drugstore, sold as a hair 'developer' or something.
Mine doesn't need any switches replacing but I took it apart out of curiosity, and it looks easy to service if you can solder.
I don't know about regular keycaps, but I know for a fact that Signature Plastics makes red esc. keycaps for ALPS, as I bought one about a week ago.
The 'skirt' of the key is a tad short, but not enough to make it look bad.
Maybe shoot them an email and ask if they can help you with the other keys too? Can't hurt to ask...