Rewiring is easy, the rears require removal of the rear seat, passenger front and rear door plastic sill plate, and B piller trim base.

Fronts require removal of the underdash panels, the rears also require these to be removed so do them at the same time.

Don't use the common ground, most new head units do not support common ground but will run like that for a while until they begin to have quality issues.

Matt.