on the rear panel. fold your seat backs down and look for screws on the panel, there are 2, one is under the plstic were the seat folds down, and the other one is in the notch where the cargo cover sits. there is a little peice of plastic were the seat belts go in on the panel, that just pulls out. there is also a plastic pin fastener close to the hatch about mid way up. after that just start prying it away from the wall. for the drivers side make sure you pull the outlet out and disconnect it before pulling the panel off. i forgot you may have to pull the sill off of the floor before taking the panels down. i can post pics if you'd like.

the front speakers are 6 1/4 and the rears are 6x9.

and no it is not ok for the ground wire to not be grounded.

and if everything was working properly prior to the install take it back and make them fix it.