How do i swap out my engine harness?

[mobbin240]

Well my engine harness as trashed on my 89' nissan 240sx and i purchased the car as a project ive made alot of progress with the car by replacing the whole interior. i also put on a turbo ready exhaust with swapable down pipes and a wideband tuner so i can install, and mount the turbo and start the car and imediatly start tuning AFR. ive already had it running for a while but i want to clean up the engine bay, where do i start?