1999 Acura 3.2 TL runs hot 136,304 miles

I just noticed today that while I was sitting at a stop light that my temperature gauge was really close to the hot side. I just bought my car a couple weeks ago and since I've had it it has always stayed below the halfway mark and the cool side. I noticed that when my car is idling it would go higher and when I'm driving at normal speeds it's a little above normal temperature, still slightly warm though. When I park and shut off my car the fan no longer stays on like it has been, but when I turn the key so the car's not on but the electrical stuff works the fan runs, and I'll shut it off and completely and I don't hear the fan anymore. I don't know if it's the fan, the thermostat or some kind of sensor/electrical problem. I'm not very car savy and I don't want to go somewhere and have them rip me off because they know I don't know what i'm talking about. Please help, Thanks.