You will need a rear output converter, it taps into the wires for the rear speakers.
Easiest way to do that is keep it in the trunk and use a three foot RCA cable.
Ground can be had anywhere on the chassis, just make sure you thoroughly clean the paint off before you make a ground. Seat belt bolts work great too.
Remote comes from any ignition source such as cigarette lighter (make sure it's on ignition though), fuse panel (wiper fuse, ignition module fuse, ect).