Yes, you can use the stock backup camera with an aftermarket radio. However, I have heard about some head unit brands not wanting to work (ie Pioneer) while others will (Kenwood, Sony, etc.) Not to worry tho' - aftermarket camera's that do work are less than $20.
That's the correct harness, but check some of our site suppliers who have it for less $. It also comes in the Schosche wiring kit if you want the whole thing to be plug and play with the stock wiring.