When you say you have worked on rifles, shotguns, and handguns, what type of work have you done?

My guess is little to none, considering your other post about gunsmithing is asking what bedding a stock, polishing a bolt, and a recrowning a barrel means.

For the SKS, there are tons of aftermarket parts available. 100% in NO WAY worth it to strip, sand, and refinish an SKS stock. Buy a $75-100 aftermarket polymer stock, especially if he's looking for that "tacticool" look.

Do not alter, polish, etc anything inside of the SKS. Very easy to make an SKS unsafe if you don't know what you're doing, and very difficult to actually make it run better unless you DO know exactly what you're doing.