Arc welders are no good for thin steel, you will blow the metal to nothing. Something like this is what you need: http://www.weldequip.com/clarke-160tm.htm
Have a good look on this site, the tutorials helped me alot:
http://www.mig-welding.co.uk/
What would be the technique for repairing the seam between the boot floor and the side wall? View attachment 114715
Is it cut out the seam, some from the floor and some from the side wall to make the seam bigger, and then weld a patch in, or something else?
Is it best done from the inside or the outside?
Is that area regarded as being close to the fuel filler pipe and tank to require it all to be removed?
I apologise to the experts here for the beginner's questions, but I am trying to get a plan in place for whether I could eventually tackle this sort of job (after lots of practice) or not.