The camera I bought came with everything I needed, including cables that let me wire it into the circuit breaker panel so it could run even when the engine is off. (It didn't work, but that was probably my fault.)

Installation was easy - glue a thing to the windshield & rear windshield, & run the wires to the cigarette lighter USB adapter (which was also included). It was a bit of a pain to tuck the wires into the trim around the doors, but overall, not bad.

But yes, it would have been easier to have a dealership install one for me.