I am interested in creating some of my own MOD files, and I have two questions: First, do I need to know how to write sheet music to create MOD files on the computer? Second, is it easy to write a MOD version of a song you've heard on TV or on a video?

No you dont need to know sheet music. Though it would make it quite easy to port sheet music to a mod. Basicly all you do is specify what instrument at what note to play. You do this a bunch and you make a mod file. Plus you have things to change tempos ect. Look for modplug its a win95 mod editor thats very good/tutorials with it.

I would recommend ImpulseTracker or (if you''re going to use a MIDI Keyboard) FastTracker 2.