okay, first do your best to remove the stock from it's origin and once you got that, put it where you want on the sig , then get the lasso tool and set the feather px to somewhere between 10 to 20 px. Then outline what you want of the stock to keep in the sig, right click, select inverse, and then hit delete. It should blend fairly well into the bg. You might have to mess around several time to get the position you want.
For fonts, check out www.dafont.com
And something to help with BGs, make a BG with black and white brushing only and then go to Layer>Adjustment Layer>Color Balance and mess around til you get the color you like. It makes it look better. Also, try Layer>Adjustment Layer>Brightness/Contrast for... well... brightness and contrast.
I think that's about it.