Couple of questions related to N64 emulator

[GAMESHARQ]

I'm looking to get an N64 emulator so that I can play WWE No Mercy. I'm pretty sure I know where I can find the emulator and the ROM, but I've heard that there are mods that can be added to the game to do things like update the game roster (character selection) and arenas (stages), etc.

Does anyone here know where I can find the mods for this and how they work? (i.e. how do I apply the mods to the ROM?)