I agree, an Accessport is a great tool to have. As for the issue of overheating when you let it sit and idle, I'd recommend
looking at your fans. I can't remember the exact temperature (somewhere between 190-210*F) but the fans should come on
at some point and drive coolant temperature back down about 20*. This should happen cyclically, as the car is not moving there
is no air flowing through the radiator, temps climb and the fans drive it back down. This is why when you are driving harder and
roll up to a red light, you can sometimes hear the fans kick on. It's not uncommon to blow a fuse for the fans. I'd check to
see if the fans are in fact turning on, if not, check the fuse(s). If the fans are coming on, but the coolant temp still increases,
you may have an air pocket somewhere in the system OR your thermostat is shot.
I hope this get's you started down the right path.
By the way, welcome to the community! It's great here. Lots of knowledgeable, respectful people.