Do you know if the gun is an R, or a V? They are all a bit different in the fitting of the stock.
If it is an R, (most likely) you need to remove the front wood (two screws, I believe) drift out the pin that holds the main spring (fits into the recess in the water table, has two serrated forks on the front) to remove that, remove the screw that holds the back of the trigger guard on, which, goes in from the top of the water table (if it is a long tang trigger guard, you will need to remove the two screws that retain it to the grip as well) remove the trigger guard, remove the screw that is behind the triggers going up, which, is threaded into a half moon shaped piece of steel that comes out from the top, and then you will have access to the stock screw. I'm pretty sure the screw you are referring to goes into the trigger guard from the top, and you can get to it after you remove the long stock screw.
If your screw drivers say "Craftsman" on them, stop right now, and send the gun to a gunsmith.
I'd work hard to make the original stock work out, especially if the gun is marked "Firearms Center Inc." on the barrels-that would be a James Wayne era import, and, not a gun usually considered top of the heap in quality. It most likely wouldn't be worth throwing a bunch of money at. If it was originally produced for the European market, quality from that era could be decent.
Good Luck.
Best,
Ted
