Guess you saw my thread:
Homelink+Mirror
Number one, it drives me batty not to know the outside temp, I had to get one with the temp but could care less about the compass. It's a package deal, you get one with the other. For me, I could not see going to all this trouble and not get the temp gauge. I did not pay close enough attention, maybe you have a temp reading on your HL and I did not.
I elected to have it done by a pro because it is under a warranty from them. I never fooled much with car wires. The needed to pull a wire from the dome and the A-pillar.
Did I pay more than e-bay? Sure I did but sometimes you just have to weigh the time+knowledge to do these things vs price.
I am real happy I had it done by a place that does all the car dealer mods for dealer installed options. They knew what they were doing and did a great job.