Welcome aboard...

>Also, my "low coolant" idiot light started blinking last week.  
>I checked the coolant level and it was well above the "max" line.  Whoever 
>filled this up must have used another input than the usual filler tank

Sounds like your engine is filling up the tank, via the pressure relief valve.
That tank behind the rear plate is an overflow tank only!! The real radiator 
tank is only accessible when you lift the engine hatch, on your left. The 
cap has a hose going to the overflow tank you have to pull off before 
unscrewing the cap. Check that tank asap! It controls the coolant flow and a 
low level will slightly affect affect cooling, unless it's too low! . Heed 
the red light, it is keeping you from going into meltdown. My '87 leaks 
somewhere, needs topping up every 2 weeks which is a pain. You should go for 
phosphate free antifreeze, Autobahn or otherwise, Sierra Eco type is free of 
phosphates I believe. I use Autobahn, and curse the price.  tim s.