I can edit pixels, colors and text - that's easy enough. Is there a program to make swapping out NES music with something else (say, composed in FamiTracker) to make it easier? I don't know NES programming like Assembler, though I'm half-tempted to learn if this is the only way to make this happen. 

No, there is no such program, and it is not possible to do in an easy way.

Just checking. Thanks!

A program like that would be possible (but fairly difficult) to make, but it would have to be specifically tailored to a specific game, similar to how many of the level editors in the ROM hacking circles can only work with one game. I haven't seen a tool like that for any game though.

Not possible. I managed to change the music for Cliffhanger after reverse engineering the music engine in a hex editor. And that was an easy one, every game has a different engine, so you have to do it specifically for each game.