jcalis! Darn it!!! No....there's really no part you can't replace, but I think all you need is the spring. Your button looks fine. When you get the springs in (order a couple/three while you're at it,) just unscrew one and put on another. Don't take the REO all apart....sometimes you can damage the screw that holds the delrin cover on and it's not worth it. The only thing you need to replace is the spring.
Rob sells rebuild kits, and somewhere way, way down the line you MAY need to, at some point a LONG time from now (hopefully) either rebuild the Grand or send it to Rob to be rebuilt, but for now, for general usage/purposes, you don't need to take it all apart. Don't.
I'm not very mechanical, but I know that messing with a multimeter and firing the REO at the same time.....somehow you can get the wrong lead in the wrong place at the wrong time so that if you fire your battery, it'll cause a short. It happened.
Well....you vaped enough on it, and held it and looked at it and played with it enough that you're hooked. LOL This is the perfect example of why we all want at LEAST two....and usually more: backups for our backups. If you had a backup REO, you wouldn't mind waiting another three days for a new spring.....you'd have a REO you could be vaping while you wait AGAIN for the mailman!
So......when you order the springs, you might as well go ahead and get that second REO......I'm just sayin'........
Jan