Hi I was wondering if anyone knows if it's somehow possible to turn one of the 2 blank slots that are next to the mirror controls into a garage door opener, by that I mean add a button there.

Step 1: buy button and speaker wire from radio shack.
Step 2: pop out the plastic blank and drill it to put the button in.
Step 3: Open your garage door opener and solder a wire to both pins of the button. Some have 4 pins in which case you will have to figure out how they are paired using a multi-meter. Then solder the other ends of the wires to the switch.
Step 4: mount the opener inside your dashboard.

Optional:If your opener uses a 12 volt battery you can tap into your cigarette lighter to power it.

^Cool