Are there a book that tells a dumbie how to operate a sound mixer
Probably. But experience is going to be your best teacher since no book out there is ever likely to talk about all the same gear as you use or be written by somebody doing exactly what you do.
The manual is usually a great place to start. Read it all through (including any technical sections you don't understand right away) and highlight anything that seems important. Then hook your gear up and do some "dry run" dj-ing without the transmitter on until it starts feeling more comfortable and you figure out what everthing does. Then try sending that out to a recorder so you can listen back to it and hear how you sound.
Probably everybody here could give at least a couple pointers on the basics of running the board. I'll give a couple of my favorites, which may or may not be something you can use.
1.) If possible, adjust your sources (cd player, tape machine, compueter, whatever) so that you have a good sounding level when the volume control for that channel is somewhere near the middle. Doesn't have to be right in the middle, but close enough you have some "running room" to make adjustments for louder or quieter material.
2.) Label your channels. Otherwise sooner or later you'll have a "braindead" moment where what you thought was on channel 2 is actually on channel 3 or something like that. It might happen anyway, even if you label.. But labelling helps figure it out faster.
Daniel
out of curiosity, what kind of mixer, turntables, tape decks, cd players and transmitter are you using? I remember the old 3 channel Radio Shack models. They were very simple and basic. That's why I liked them. I also prefer the analog VU meters over the lighted digital ones. I like stuff that just looks like a radio station. I also prefer the slide rule potentiometers as opposed to the round knobs. When I did radio, I used the knobs and the slide rules.