93 Century-Intermitant Starting Problems

Please can someone help. I am have problems with intermitant starting. Car runs very well, but sometimes when you turn the key, it cranks like a jack rabbit, but won't start. If you wait it out, usually no more then 5 minutes tops, and keep trying, it will eventually start. It seems to happen every couple of weeks, and does it maybe 4 or 5 times, then is okay again for another 2 weeks or so. The service engine soon light comes on, but also not always. How do you check the service engine soon light to find out the code?
I have replaced the Coil Pack, had the fuel injectors cleaned, replaced the gas cap, changed the plugs and wires, pcv valve, fuel filter, and fuel pump. Am about to have the fuel regulator changed, and am considering having the crankshaft position sensor done.
Being female, I don't know a whole lot about the workings of a car, but am trying to learn fast. The car is in beautiful shape, and has only
143,000 KM's on it, but I am beginning to wonder if it's really worth all the hassle.
Can anyone help me?

The following link tells how to pull the computer codes off GM vehicles (and what the codes mean):

http://www.geocities.com/dann8785/serviceenginesoon.html

Yogi-123rd
Thanks so much for the help. Will try this and let you know how it goes.