My 2 cents:
You probably won't have to do much inletting on a GPR kit, so you may not need a whole bunch of chisels. A 1/4 straight chisel from the hardware store should be enough, along with a stone to sharpen it with as needed. On my GPR kit, the main wood work was fitting the buttplate. A 4-in-Hand rasp and half-round file worked fine for that. The lock, barrel, trigger, etc., should fit pretty well with just a bit of touch up.
Inletting "black" isn't very good for walnut stocks like the GPR, its very hard to see. Zonie is right, snag some cheap lipstick from your womenfolk or have them buy you some. Or you can buy your own... you might as well get everyone used to the fact that you will be purchasing lipstick for inletting and hanging around fabric stores to buy patch material, etc. I'll leave it up to you whether you want to explain your purchases, and to whom. :grin:
IIRC, most of the holes were predrilled. I just used a standard mill file and various grades of sandpaper on the barrel.
If you have some tools already, it might pay to wait until you get the kit and take a look-see to pickup whatever else you might need. The hardware store is fine... but don't overlook junk stores or pawn shops for smaller things like screw drivers and files... I have picked up some of my best screwdrivers and files from those places... sometimes a handful for a few bucks. I have found several good old wooden handled screwdrivers that clean up nicely and can be easily ground to any size.
Ditto for LMF browning solution. It is very easy to get good results if you FOLLOW THE INSTRUCTIONS. My only common suggestion with LMF browning is don't over finish the metal. 180 or 220 grit is more than enough. It seems that the smoother the finish, the slower things are to brown. This also saves you some work.
Also, search the forum for posts on Great Plains Kits. There are lots of posts and pictures to give you some ideas on things to do and what others have done to customize their GPRs.
Have fun, and post some pictures!