First, the bore. (check to see if it's loaded, then...)
It's easy for folks to find an externally good TC rifle with a roached bore. The easiest way for me to check the bore is to put some foil over the base end of a spent .223 or 9mm cartridge, and drop it down the barrel with the base of that cartridge toward the muzzle. Then a simple flashlight will reflect enough light from the foil and I can see if the barrel is pitted or not. Even if it's pitted, you've still got some potential.
Second, the lock.
Thompson Center flint locks tended to eat flints as the geometry was slightly off. Not all did it bad, but enough that the cock was switched over. Depending on when your rifle was made, it may have been upgraded at the factory, especially if it's a Renegade with a synthetic stock. Just double check though.
Third, the stock, as you mentioned.
Track of The Wolf still shows upgrade stocks for the TC, half stock, octagon barreled rifles. Right now the stocks made for 15/16th width barrels are not in stock but you could contact TOTW and see how long is the delay. IF you are lucky and your rifle barrel is 1" wide, then they list at least one stock for that barrel in stock.
TC Replacement Stocks
IF it was me and I was going to all that trouble, I'd wait for the plain, maple stock, and THEN I'd swap over the parts, but I'd do a faux striping on the stock as was often done with plains rifles, OR simply use the least expensive stock. The faux striping has been discussed on this forum many times and there are excellent tips on how to get it to look
right for the time period. Personally, I don't like the faux stiped look on any rifles other than half-stocked plains rifles and reproductions of trade rifles.
So back to "first"..., IF the barrel is pitted, it still might shoot well. If it's badly pitted, but is priced low, then you can either have it reamed out to .56 caliber smoothbore, and have a gun that does both round ball and shot, OR you can have it recut to .58 caliber.
LD