Brian - you're doing the right thing by starting with a kit - don't skimp on price, the reputable suppliers will be in the range of $500 - $700 for a good pre inlet stock and quality locks and other parts. Doing a kit first gives you a good sense of what it takes to have all the parts placed to make the gun balanced and function well. Then you can go to the next step and do one from a blank, but there is a lot of inlet work building one "from the board". Tenesee Valley Muzzleloading in Corinth, MS, Pecatonica River supply in Illinois, and Cabin Creek Muzzleloading are three of many good suppliers out there, and their pre inlet stocks have a very good reputation - there are some problems if the stock is not pre inlet well. Track of the Wolf carries a huge inventory of parts. All these folks have websites, and I would contact them to check on availability of barrels, etc. In my opinion, Jim Chambers makes one of the top quality locks out there, and also has kits.
Give me an email at email@example.com
if you would like - I'm not the most experienced builder out there to be sure, but have made a few from scratch and have had some fun blowing off a few rounds.