I'll pay you 3 Euro right now!
Here's my thread on restoring an XT 83 key. The below might help you:
* fohat's guide is extremely good. The most important thing for me was the section regarding clamps. You. Will. Need. Them. I didn't buy the much more legit ones that are in fohat's thread, but just the plastic ones from Amazon. They were cheap and I don't really plan on using them again.
* Wiring up your own Soarer's Converter is not strictly necessary. They are available, pre-made, on ebay. Just search for them.
* IIRC, the blue legend caps are kinda uncommon. That might also boost value.
* I didn't use a wooden frame. I just used a couple of dictionaries.
* I have two different barrel plates (bought an extra, just in case I screwed up). Both badly rusted. I used a 24-hour soak with Evaporust, followed by two coats, front and back, of Rustoleum Rust Reformer, followed by two coats, front and back, of Rustoleum Primer + Paint. Both turned out great.
* If your springs are badly rusted, as mine were, you can try Evaporust. It ... worked poorly for me. I ended up buying all new flippers and springs. That's about $1 US per.
* If you have an ultrasonic cleaner, it's an excellent way of cleaning keycaps. I use a couple squirts of Simple Green, if the keycaps are really bad, for 16 minutes. If they're not really bad, effervescent denture cleaner works extremely well. This would also get rid of the pencil marks. I generally use 40C to 50C heat.
* If you need a template to make a new foam mat,
go here.
The case is likely to wipe clean with a mild detergent. I have used the Mr. Clean Magic Erasers for really tough spots, but please understand that the Magic Erasers are really just very fine sandpaper sponges.
If you are overwhelmed with this thread, you can post it for sale here and someone will buy it. Just look for closed auctions on ebay and decide on a decent price. I'll be the first to say that unless it really is $3 or 3 Euro, I won't be buying it.