Its pretty straight forward really, I had the bumper off to do my lights so getting the cables through the grommet and into the boot was easy but I can imagine that bit to be fiddly if the bumper was fully attached, you might need to take a few bolts and clips off to get some access.
Other that that it's just the yellow video cable to the back of the head unit, tap the power cable into the reversing light power cable and the earth to a decent earthing point and run another cable from the reversing trigger on the back of the head unit to the reversing light power cable.
There's a good guide on here somwere, very detailed and pictured.
I've worked with cars for the last 10 years and that's the 1st time a blown reversing light fuse has prevented a car from starting!
Your always learning in this game haha.