A:AnswerI would make an appointment to have best buy take a look at the wiring. It sounds like something must be wired incorrectly or you have a loose connection somewhere
A:AnswerGo to the Kenwood site, watch the overview video. At 1:33 in to the video, it appears it's as simple as drag & drop.
https://www.kenwood.com/usa/car/navigation_multimedia/dmx4707s/
A:AnswerBased on the vehicle it will be installed in you will need harness/plug/connector attachments. BestBuy sell these, Look at Crutchfield.com to get an idea of just what you need and you can then purchase from BB.