Ok, sounds like we have an intermittent problem. When she won't start the first thing is to check for spark. Either pull a plug wire and buy a spark tester, or if you have a timing light, install the pick-up on any plug wire and have someone crank while you activate the timing light. No light, no spark.
No spark, start with checking for bad grounds, then you can try a new HEI module. The system is simple, unless you have some wiring issues you should be able to diagnose it.
