Often the CRT monitor goes bad. I'd not pay $300 for a new monitor/camera system, there are many choices available on Ebay, Amazon, etc. that cost far less. Your camera is black and white, 102º wide coverage. Check the number of wires in the present camera run, you might have to cut and splice new ends on the cable, but you probably won't have to run a new cable front to back.
I replaced my B/W CRT with a 7" color monitor. It had two video inputs, so I added a side camera to eliminate the right side blind spot. Not a difficult project and it's nice having a 'wide' view color dash monitor.
Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI