Quoted:
I know two things for sure if your buddy wants to sell that gun:
1.) 99% of collectable gun owners/buyers do NOT want aftermarket parts in, on or with the gun.
2.) To reach the population who desire the gun and get the premium price it is necessary to contact a reputable networked and trusted agent who can get the most for your firearm and you will pay (not cheap) for his service.
I say this only because of the risk in using it (and other old firearms). Hope things go well, especially if you and your buddy decide to keep it.
V
OUT
He wants it for fun, maybe a little small game, or backyard trap. Based on what little research I've done, it looks like he'd be limited to very light loads in the gun. With how chewed up some of the stock is and that currently it doesn't work, I'd just use it as a rustic wallhanger.