Welcome aboard Aaron_y.
Welding, and metal working in general are good skills to have in life. If you look around, you might be able to find evening classes somewhere. I know there are a couple of career training centers near me with classes a couple nights a week at a price way lower than going to a year or more of a trade school. Here’s one in my area to give you an idea.
https://www.rctcerie.org/programs/welding/
But if you want to dive right into gasification, check this thread out.
As for working on engines, start with a small motor that’s easier to tinker with, and cheaper to replace if you gum it up with tar. Predator engines at harbor freight are nice and cheap, or keep your eyes peeled for push mowers being thrown out. 9 times out of 10 they only need a new spark plug.