I'd figure $400 to $600 as they aren't very hot right now.
There are plenty of them out there in that condition in that price range, but none of them seem to be moving- at least in my area.
There is a chance you could just get the forearm matched up pretty close and not have to replace the stock...try Macon Gun Stocks- I've gotten several stocks and forearms from them for 1897's and model 12's- even a nice straight gripped English style stock I put on a 16ga model 12 for upland hunting- if I ever get the chance to go.
They were semi-inlet, so I had to fit them myself, which wasn't hard to do and I learned quite a bit- go slow and it'll be fine.