As far as hand tools go for sheet metal fab, in addition to Eastwood or Snap-on check out
www.autobodyhandtools.com . You'll definently want a few body hammers, (the vertical or curved chisel and pick hammers I find to be the most versatile). A few dolleys (the metal blocks), A General purpose/Universal dolley, a Toe dolley and Heel dolley are all nice ones to have(you can make your own out of pretty much any solid block of steel, i.e peice of rail road track. A spoon or two are nice to have around as well as a slapper(wood and/or steel) A shot bag and plastic mallets will allow you to get pretty crafty. Left, right and straight metal shears are very handy. A torch is usefull for anealling metal and heat shrinking. Forms/anvils are very usefull things for shaping simple curves, A steel tube or pipe can be easily used to creat radiused bends. Most of these tools can be made at home or you can improvise a bit and use regular shop stuff as shaping tools (i.e two peices of angle iron clamped to a work bench can be used as a sheet metal brake). There are ton of very cool, but $$$$$$$$$ bigger metal fab tools out there, but you can do almost all the same things with the previously mentioned tools and some determination coupled with patients. Before you even bend a peice of sheet metal a collection of drafting/crafts/layout tools are a mandatory: a compass, scribes, sharpie, squares, rulers, tape measures, card board/card stock for templates, etc, etc. It pays to make a template(s) of what you want to fabricate out of cardboard, card stock or some heavy construction paper, make all you sizing/adjustments with the template then use it as a guide when working the sheet metal.
You said you have access to MIG & TIG, use the TIG as much as possible, it produces a softer weld, thus you can go back and hammer on dolly the weld bead to smooth it out a bit; MIG produces too hard of a weld to do this. Gas welding produces the softest weld(that I know of off hand) but has a huge heat affect zone thus it's easy to warp the hell out of your sheet metal; that said you can hammer & dolley it back into shape in most cases with out much trouble. A few of the old-school hot rod guys do a lot of gas welding on sheetmetal, Gene Winfield and George Barris(both respinsible for countless movie cars and famous street rods) among others; their work speaks for itself.
Sheet matel fab is a very rewarding(not to mention satisfying) set of skills, it's kind of like creating functional sculture.