First on the finish, there are some commercial "touch-ups" available which work OK--sort of. You need to know what kind of finish it is--blued, parkerized, painted, etc. to select the right product.
As far as upgrades, aside from changing springs, which is something you should do first off, and changing grips, there isn't too much else that that you should tackle until you become a little more familiar with the pistol. I'd shoot a couple of hundred rounds and determine whether the pistol is functioning properly--feeding, ejecting. As far as the springs are concerned, change the recoil spring to whatever is standard for that configuration. If it's an older piece, the spring is tired. It may have been changed out by a previous owner, but its nice to know what's in there. The firing pin spring, and mainspring, can wait, although they are easy to change.
Learn how to field strip, lube, and reassemble without incorporating the hated "idiot scratch". You'll probably need someone to show you that one. Don't learn the hard way.
You can call SA Customer Service with the S/N and they can tell you the born-on date and what model it is. It sounds like you've found a nice interesting piece. Enjoy it.
Aside from this forum, 1911forum.com, and 1911.org are good additional forums with lots of opinionated know-it-alls like me.