Killer price! All you need (other than a 3" chambered barrel) is to replace the 2.75" ejector spring with a 3" ejector spring. Any good gunsmith should be able to do this job inexpensively. They should also have a Remington ejector rivet tool kit (from Brownells) "just laying around". If they don't know what you're talking about when you mention rivets and swapping ejectors, then run. Run and find another smith.
It's very unlikely that shotgun left Remington with that folder on it, but a free call to verify wouldn't hurt anything. It would only add value to be in complete original factory configuration with a folder. Barring that rare possibilty, mod away to your heart's content.
Just don't go "full Bubba".
"Never go full Bubba!"
The Rem folders look cool, but they are uncomfortable when firing (compared to other options like the Sage, or M4 stocks).
If you want to flip it for profit, just put it in "Terminator 2" config, and bring it to a big gun show.