A bad head gasket won't stop the car from starting, so you likely fixed whatever that small issue was. In the early stages of head gasket failure on these cars, they can run just fine for a few days at a time until enough exhaust gas escapes into the cooling jacket to cause a spike in the temperature gauge - the probe is on top of the thermostat housing near the cooling system bleed screw. Over time though, the leakage worsens and it starts indicating erratically or hot all the time. By the time the leak is really bad, your cooling system will have enough rapidly accumulating pressure to start stressing any weak links like rotting hoses or a weak radiator, and you end up stranded on the side of the road.
The high idle issue is likely a separate problem.
Sorry for the bad news, but I don't think you're out of the woods yet. :-(