Got a "new" to me Remington 20ga - rusted

[fastsrfr]

While at my wife's uncle's place yesterday, he casually asked if I wanted a shotgun. Like, out of left field casually. I hemmed and hawed a bit because he said it was worth a lot of money and he has two adult children who might appreciate their dad's shotgun. In the end, I took it home.

The thing is, this shotgun was kept in a gun case in a barn. I have no idea when it was last fired or maintenanced but I am guessing at least a decade because it has surface rust everywhere. It seems to function fine, though I haven't attempted to put a shell through it and will not until it is inspected by a gunsmith.

It isn't worth a lot. Just your standard Remington pumpgun. He thought it might be valuable because he wasn't sure they make pumps any more. Any suggestions as to how I might go about cleaning this thing up a bit? Or if I should even bother?

[CHEMICAL]

Eezox and a rag on the outside, same solution with a bore brush on the inside. If it's smooth bore best way to clean it out is probably to just fire away.