Hi Insane3082,
A water pump (as Mike suggests) really has nothing to do with the engine firing up. In fact you "could" take off the belt that turns all of the componants (AC/Alternator/PowerSteering) and it should start up. I'd not run it for very long under that senario.
But, you need 3 things for an engine to run.
1. Spark 2. Fuel 3. Compression (ok, could be expanded here, but)
To determine if your getting spark your best bet is to wait for a dark night (or dark garage is accessable) take one of the spark plug wires off, lay it next to a grounded area (most metal areas will yeild this like the alternator bracket) and have someone turnover (try and start) the vehicle while you watch that spark plug wire. If you have spark you should see an electrical arc from the tip of the end of the spark plug boot to a ground, sort of like a mini-lightening along with a poping noise. If you don't chances are its the ignition. CAUTION DO NOT TOUCH/HOLD the sparkplug wire or boot while doing this, it'll shock you into next week.
Fuel can be a little more tricky, depending on your battery life. If while turning over the vehicle several times, have (again) someone else turn it over. Place yourself at the end of the exaust pipe. Using your hand wave up from the tail pipe (while it is being turned over) an smell. If it smells like gas, faintly, than your getting gas too. If not, cover the tail pipe with your hand and verify that there is pressure/air pushing out. If that is not the case than you either have 1:a major exaust leak 2: a major mechanical issue (timing chain) with the engine. If you suspect an exaust leak, the only way to verify gas is getting in would be to verify (as mentioned before) fuel pressures at test points on your engine. I guess one "could" take out a spark plug and turn it over and again sniff for a gas smell, but I would caution that if in an enclosed space (Garage).
In short, changing the water pump will do about as much as changing the air in your tires for this problem.
Cheer
-Joe