How do I change the timing belt and water pump on a 1994 Toyota Camery with a 4cyl eng.

I recommend that you have it professionally done--many do-it-yourselfers try and fail, damaging valves, pistons, and egos in the process. If you are determined to do it yourself, here's the best general advice I can give:

Place a mark (e.g., Whiteout or white paint) on each pulley and corresponding point on the side of the old timing belt, before removing. Then, remove old belt, transfer marks exactly to new belt, and reinstall with confidence.

I agree about the pro's doing it. Just too big to tackle in the driveway. And the tools needed... well, let's just say there's a lot of special tools and knowledge needed for this job and leave it at that.