I'd have to check, but way back when, San Diego had adult classes in welding and machine shop at the City College.
I took welding there while I was in grad school at UCSD. Machine shop is somewhat easier - you can almost "read and do."
Serious O Scale locomotive builders do have machinery. I have an 11" Sheldon in the garage, a 9" South Bend in the Cub hangar, drill presses practically everywhere including two in the kitchen, oxy-acetylene, and a Bench Master end mill.
Sarah is an artist. You do not need to be that good to build locomotives.