1992 Geo Prizm Does Not Start

My 1992 Geo Prism randomly has not started on an average of once a month since April 2009. The only pattern I have noticed might be a coincidence. The car hasn't started on really hot days (Tampa, FL) and when the car likely has been equally hot. The key will turn over, the dash lights will come on, but the engine simply doesn't even make a noise. Several hours to the next day later, it will start without a problem. When mechanics test it, they obviously cannot duplicate this random problem.

I read on another website about a 2004 Civic Hybrid having a similar problem, but with the engine coming on after up to 10 turns of the key. The problem someone suggested that this car had was either an ignition switch or a neutral switch, to include the latter being out of alignment.

I noticed somewhere on this website, someone suggested the engine not turning over could be due to several problems. They noted it could be the electrical voltage system, starter voltage, neutral safety switch/clutch safety switch, anti-theft (I don't have this function), or internal engine damage.

I have noticed the neutral switch is the commonality between the two responses I have noted to the engine not catching when the ignition switch is turned.

1) Since the batter, alternator, and voltage seems to be okay on my car, what is the probability that my Geo Prism problem is caused by either the ignition switch or something wrong with the neutral switch, or the neutral switch's alignment?

2) How much should I expect to pay for parts if I were to request that the mechanics replace the neutral switch and ignition switch?