how to replace a water pump on a 1996 plymouth neon
Purchase service manual for 1996 Plymouth Neon (Factory, Haynes, Chiltons, or equivalent).
Read through procedure in manual.
Purchase, borrow, or rent tools necessary for job.
Carefully follow instructions in manual and replace water pump.
Take car to mechanic and write check for repair work.
This job is basically a timing belt replacement, with the water pump service tossed in because the two jobs are always done together. Here is an illustrated guide: http://jball.neons.org/howto/timing_belt/howto.html. After reviewing the hellacious instructions you may decide to bring your car to an experienced mechanic rather than trying to DIY.