Farm and Workshop Welding: Everything You Need to Know to Weld, Cut, and Shape Metal
That is a good book about welding. I haven't welded in about 20 years myself and need to relearn how. I never was good at striking an ark but after that I was ok with a stick. I think I will be looking into a mig. I used a friends mig once and it is really easy compared to stick. I do have an old Lincoln tombstone kicking around.
As to the batteries I agree you don't want to buy the one at a time. I would try taking to your mechanic he could probably get you a couple of batteries that cars reject but are ok. It wouldn't be more then an experiment base because you want deep cycle or fork truck batteries car batteries just don't have the cycle life.
Around here once you sell something for scrap they can't resell it. Some stupid law. Some yards might turn a blind eye to your driving out with less weight in the back of your truck then you drove in with but they don't want to get caught or known for it.