As above, SteveP guide tells you everything you need. SteveP used to make those wiring looms (for a small fee) so all you had to do was fit everything, but I don't know whether he still does them.
The eBay ad suggests all he is selling is the camera plus the video lead that runs to the rns510 but the picture has other wires wrapped around the video lead, so it's difficult to tell whether you will need to get a wiring loom as well or not. As the seller is selling this for retrofitting to a mk6, even if it has everything you need for a mk6, the loom for a mk5 is slightly different. I think it's only the connector for picking up the reversing light signal which differs (assuming the sellers wiring picks up the reverse light signal in the boot lid).
Think the best thing to do is to get the seller to confirm exactly what cabling you're getting for your money.
