I've bought cameras and monitors from:
Backup Camera System | Rear View Backup Camera | RearViewSafety.com
and cut and spliced cables for my motorhome. There are cheaper ones available on ebay and amazon. Most of these backup cameras have infrared leds to give you night time vision and should work in an engine room just don't put the camera behind clear plastic (blocks the infrared leds and just gives you glare). Some of the cameras and monitors also have a switch to change from mirror image to regular.