I installed a power seat to the passenger side of my truck. It already had a power driver's seat and heated seats. The wiring was in place as far as the center console. I fabricated the intermediate harness that connected to the switch module. Overall a great mod since it made my better half happy.
Since the tricky part of the wiring is incorporated in the switch module, you basically just need to provide an adequately fused power wire and ground. Be careful working around airbag sensors and disconnect your batteries a few minutes in advance to disarm the airbags.
Dan