Bad news, everyone.
Brought the Mossberg into the gun shop/range and the gunsmith looked over it. He tried his perfectly-fitting screwdriver and tried his best but, apparently I'd stripped the damn thing. So he gave me the options.
Drill out the screw and remove it, for $40. It was hard to reach, and he would have had to be pretty slow and delicate, not to mention the force to take it out when it's stuck so bad.
Saw the stock down to a pistol grip to remove the screw; the pistol grip would be salvageable, but the stock would be useless, for less than $40 (exact price not mentioned).
Keep it as is, leave wood stock on, for the $50 spent on the now useless new stock.
So as you can see, there was no good option. I thought about it for a few minutes, and I'm not proud to say I picked option two. I love the wood stock, and have nothing against wood stocks. I think it looks great, and it hurts to think of the gunsmith hacking that nice-looking stock off. But I didn't see myself putting the wood one back on anyway, so it likely would have sat in a box somewhere, "Just in case I ever feel like putting it back on." At least I should be able to have a wood pistol grip I'll never use. Easier to store... And the guy's going to install the new parts. Wish I'd not lost the orange magazine tube follower I got from Midway USA, could have had him put that in, too.
