yeh that'd be the way to go, get what he can for it.
Sometimes its the basic checks they dont do that lets them down. I had a VX Executive with a genuine SS bodykit, FE2 and most of the SS interior (ie dash cluster, dash surround etc). To the untrained eye it looked like an SS.
They valued it based on being a VX SS not a VX Exec so naturally they over valued it, which was fine, thats what I needed to be able to buy the VZ. Signed the paperwork, deal was done. They went out to start it to move it from the carpark and, oh, wait for a LS1 it screams like an Ecotec.
Popped the bonnet and ... oh tis missing 2 cylinders :whistling
But im curious whats caused your mates car to rust like that????