romhacking.net is very useful. Start with the easy systems first like NES/SNES (Really easy), then advance to maybe GBA or something (Alot harder than NES/SNES hacking, mind you..). Done that? Start learning MIPS ASM (I seriously recommend learning this), learn to use hex editors (You'd prolly have some experience with this from NES/SNES/GBA but read FAST6191's useful guide). Learning to program is useful, but not a necessity (So you can program your own shit to edit game scripts and stuff, somewhat like what you mentioned about a software translating MHP3). Knowing how to debug is great when your stuck somewhere and need to find a pointer responsible for line length and stuff blah blah blah (rants on).
But seriously. Once you get the gist of hacking basic systems, you can come back and ask.