Here is an old thread showing the Pex striker mod
To determine how the hinges are, with the door open try to pick the rear of the door up. If they are tight it will have minimal movement up and down.
As far as a welder is concerned, you’d probably want a wire feed (mig) machine. A gas capable wire feed welder can do both solid wire (gas) or flux core (no gas), simply change feed roller and reverse output polarity.
Flux core generates its own shielding gas, like stick welding, but will have more spatter and is ‘messier.’ It does, all things equal, burn hotter than solid wire does so you can get a little bit more penetration than solid wire. Totally possible to do sheet metal, but there is certainly some learning curve (this is true of any welding process, practice, practice, practice!).
These days with the IGBT inverter technology, there are a lot of affordable, small, and quite efficient machines available. A lot will do dual voltage, 110 or 220, very flexible on power requirements.