If it's an Yellow RCA jack as mentioned, just pick one of the video inputs available to you on the new set, you might have to tune the TV to that video input for it to work, it wont switch automatically.
If it's a coax connector, then you might only have one input on the back of the new LCD and it's reserved for cable/satalite input.
I would read the quoted posts mentioned and put in a small dash mounted unit for the camera to dispaly as needed, then the problem is solved.
Monty & Janet - 2007 Alpine APEX 40 MDTS
S/N - 75715 - Retired - Master Certified RV Tech