I didn't know much about welding either, except for a semester in high school, over 40 years ago...all stick welding then.
I bought a Mig and there was plenty of learning involved, but the end result was worth it.
There are others who have done excellent work on badly damaged or rusted tubs, but here is my effort.
http://www.cj3apage.com/cgi-bin/3Ayabb26/YaBB.pl?num=1360037699/allLots of good advice and info from other CJ-3a forum members..
If you do buy a tub, keep your old one until the new one is fully installed. You never know when you may have to measure for a hole or find an original bracket that still may be on the old tub...
Randy