Well, yes, based on a recommendation I was looking at Pecatonica for a kit... Are the kits from dixie gun works simpler? Is a walnut stock acceptable for someone who owns a curly maple?
Pecatonica River kits are great, and I think Captchee pritty much covered what the "biggies" are to assemble one of them.
If I might elaborate a little on what he posted by picking just one of the many things he mentioned:
Most of the "furniture" like trigger guards are sand castings. They require filing, bending or straightening (sometimes a lot!) multiple sandings and polishing before you can begin to inlay them into the wood.
Inlaying a trigger guard can take me 1-6 hours depending on the shape of the finials. These are usually held in place with small pins. Drilling the holes for these can be a chore in itself...
I could go on, but suffice it to say: I think that you could make one of these, but IMO it would take a lot longer for a first time builder than the 2 1/2 months left until Christmas time.
That time limit and the fact that this is your first home built gun is the reason I suggested one of the Pedersoli Kits from Dixie.
They are pretty much fully inlayed for the lock, the trigger, the trigger guard and the holes are drilled and threaded for the screws.
In other words, all of the things that take a lot of time are already pretty much done for you and require only a little trimming/cutting/tweeking to get the kit assembled. This leaves plenty of time to sand, stain and oil the stock and to lightly sand and finish the barrel.
As for how fitting is a Walnut stocked pistol for someone with a Curly Maple rifle?
Many of the surviving pistols from the flintlock age have Walnut stocks even though most of the rifles from the same era are stocked in Curly Maple or Cherry.
Sure, a wealthy person might have had a matching pistol made to go with his rifle, and indeed I have made a matching pistol for a CM stocked rifle but I don't think it is really necessary.
IMO Walnut would be fine.