First of all, even with the problems you mentioned, you stole that thing!
If it were mine, I would just replace the safety and stock, get an 18" barrel,
and put a decent light on it. Refinish with Krylon, and you have yourself a
really great, cheap, tactical shotgun.
The Hogue stock you mentioned is perfect. If you're really going cheap, just
cut down the existing barrel. There are plenty of threads here on how to DIY.
I have a Sure-Fire G2 on my 870 I got the light, mount, and 20 batteries for
less than $80 I've beat the shit out of it, and it still works.
Krylon is actually a surprisingly durable finish, for something that costs about
$4 a can Get one of the outdoor or all-weather types, and put on a few coats
I did mine this way a few years ago and only rarely have had to touch it up.
Good luck with your project, and congratulations on the new shotgun!