All i did when i cut my doors was cut the top line (where the hinges go) first and then i welded on the hinges. Then we cut down the sides. then we welded the 1inch flap or strap on both sides, then we cut the botom and the door opened.
As for the hinges i got mine at norco welding supply, they cost 3bucks and are reted at 300lbs per pair. My handles i got at my local army surplus store, they are a big alen wrench with a screwdriver type handle, they where 2.50.
I have also seen guys use welding hammers for handles.