hi all you would be welders i have been welding for 35 + years if you are going to buy a mig welder buy a fan cooled and at least a 130 amp a 180 if the money will strech this way you can welded up to 6mm safely and go to boc or the other and hire one of there smaller bottles with some practise you will be wilding stainless exhasts and the likenow if you want to be a real welder you should learn to weld with a stick plant thats where the skill is and the money.any one can weld with a mig it is a no skill welding as the machine dose the work,
don`t think i am puting you down i am not it`s just that welding with a mig is so easy and with that practise you will get great results.
as for seam welding to me thats a fars i weld thing that carry 100 tonn anw never weld all the way round as it promotes cracking metal has to be able to move and flex seam welding is done on rally car but a rally car has a really hard life for a short time so it needs to be seam welded. (this should get the talk going)
yours arch