I much prefer to make my own harness with a simpe relay and fuse or circuit breaker. It's not a true plug and play. It could be, it comes that way from the factory, but you don't want to run 55w HIDs through the factory wiring, especially with the known weak connectors.
35w HIDs should be fine with factory wiring. 55w you'll want to run a harness or relay.
Besides that, yeah, mount the ballasts and the bulbs fit right in.