Thanks for the reply. No, I haven't tested the ECT sensor or used a scan tool to read the temp. I should be able to borrow an OBD2 scanner, but I'm not sure about testing the ECT sensor. Is that something best left for a mechanic? Could I do it with a multimeter, or would I need a specialized tool? The past few years I've been trying to as much maintenance myself as possible, but I admit there are some things a mechanic should do.
Regarding the temperature gauge. Mine has never gone to halfway in the 10+ years I've had it. It has always sat around or just below 3/8. Right now it sits exactly at halfway most of the time and goes slightly over sometimes.