Hi Knapper,
Welcome to ALR. My first build was a "kit" from Pecatonica and it was a great experience. They offer a quality product and, in my opinion, offer excellent service. How hard are they to finish will depend on your level of experience with woodworking and metalworking. Pre-inletted stocks, whether from Pecatonica or any other supplier, will require final inletting of the various parts. Metal parts will need the casting lines filed off, the barrel will need dovetails cut for the mounting lugs and sights, holes will need to be drilled, and so on.
I would suggest you get one or more of the books on building longrifles, if you haven't already. My favorite is Recreating the American Longrifle by William Buchelle, George Shumway, and Peter Alexander, but The Art of Building the Pennsylvania Longrifle by Chuck Dixon and The Gunsmith of Grenville County by Peter A. Alexander are also very good. I have all three.
Good luck, go slow and have fun. And when you get stuck, do a search on the problem here on ALR., someone has probably been there and done that before. If not, ask here and you'll get some great advice.
-Ron