I don't know the specifics of your vehicle, but
- I used a fuse tap and fitted it to the internal fusebox under the glovebox. A fuse tap creates a new circuit just by slotting an adapter into an existing fuse slot. (Think plug and play) A multimeter and $20 of parts, job done in 5 mins.
- GPS will give you location and speed on your videos. If that's useful for proving who/when/where/why then yes. Personally I wouldn't have a camera without it. You only have to see videos where people comment "oh you were going too fast/slow" to see how a measured calculation of distance over time doesn't cross the mind of a layperson/insurer.
- Class 10 are not overkill. I'd look a Ultra High Speed Class 1 instead x300 premium or x600 ultimate - pier28 sells these.
Thanks! The fuse box is at the rear end of the car. It is probably more the work of hiding the cable under the head liner.