I use gas way more then I've ever needed to use TIG.
High-Temp silver soldering with a tiny torch tip is one of the most often used welding methods in gunsmithing.
And you can't do that with a TIG welder!
Next to that, manual lathe & milling maching work will be the things you need to do most often.
You do need more then a passing grade in reading micrometers, dealing with very small parts tolerences, and wood & metal finishing.
You don't need AutoCAD and 3D graphics rendering unless you work designing guns for a company that makes guns from raw materials on CNC equipment.
Most small gunsmith operations don't ever have access to, or a need for that.
rc