I have a 04 Silverado LS trim Z-71 option extended cab. I would like to install factory upgrade seats, front and rear. Currently, I have cloth bucket, drivers side power, no lumbar, no heat, no power recline, totally manual passenger. I would like to install a set of 8 way power adj leather on each side. My concern is the existing wiring harnesses under the floor and in the door panels. I am sure I would need the switch that goes in the door panel, but is the harness in place? Anything else I should be aware of?????Any help would be appreciated. Thanks, Frank