Automatics may be cheaper, but any 16 year old automatic is gonna be a huge gamble. And you must use a 1994 or earlier trans, as the newer ones are different. There's not really any way to tell if it's been maintained or how long it will last. I would plan on rebuilding it regardless, which would definitely not be cheaper.
But if you still want to do it, you can search here for auto to manual swaps (Many here have converted auto to manual, not too many have done the opposite) and see what's involved. It's essentially the same, except instead of swapping auto parts for manual, you're swapping the manual parts for auto.
Some parts you'll need that I can think of off the top of my head...
Steering column
Brake pedal assembly
Floor plate (to cover up the shifter hole)
Computer
Some wiring