Why use a gunsmith.....??? Take the ramrod and put it down the bore and measure with your finger at the rear how far it goes to gague FIRST OF ALL if the breach is properly placed.
Then take yonder dremil with the proper sized bit "start small" , Use a marker and mark the spot you want to drill, take a nail and a hammer to mark the spot and then drill the hole........
I have done it dozens of times, pretty darn easy, I cant imagine what a "smith" would cost you to drill the touch hole???
After that pop the barrel out and take some tube measurements , strap it to a stout log or tree out in the bush and load and fire it a few times and measure it again.
Sounds far more complicated then it is....Its totally easy, save your money for the 30 bucks a lb goex.