Drilling should not destroy insulation. You will lose a little when you punch through but it will be negligible if you are careful. Just push it to the side as you go through the other panel wall.
Steve has doors for all models except for the 3.5 and the 5 in stock and pre-drilled for the smoke generator. They are in limited supply right now so not listed in the site. But he can be contacted via email for a door if you want one.
The smoke generator will hold 2 lbs of pellets. He has exceeded 7 hours of smoke. He will include 1 lb of starter pellets. The pump is included in the price for the generator.
The generator is 3 1/8 inch square and 10 inches tall. The tube is 3/4 inch diameter and extends 3 1/2 inch into the smoker.
Also, Steve has held prices through all the trade talks but come 1 Oct 2019 you can expect prices to go up if the 25% tariff kicks in. So waiting for any specials on smokers or accessories might probe futile.