warranty repair questions

[BOOST26]

Hi All, Just after some advice as I really don't know much about this sort of thing.
So a mate of mine who is fairly mechanically minded purchased a second hand Nissan(2007 model) from a Nissan dealer a few months ago for $25k+.
It came with 3 months warranty.
After about 2 months he booked it in to the dealer for some warranty repairs. Dropped it off with a list of problems and the dealer said no probs.
One of the items related to leaking auto trans fluid and a transmission related error code he found with an OBD2 scanner.
The dealer calls him and says auto is stuffed. This was 5 weeks ago and he is still waiting for the car to be fixed and returned.
He is continually calling them and thinks he is getting the run around.
1st week, waiting for warranty department to approve rebuild or new trans.
2nd week has been approved for rebuild.
3rd week, car was dropped off at trans specialist for rebuild.
4th week trans was rebuilt but has some unknown electrical problem
5th week they are still trying to work out electrical problem.

I told him I think they are stuffing him around as I cant imagine it taking 5 weeks to fix a auto trans problem but not too sure what he can do.
Any suggestions? Where does he stand legally? He has had to hire a rent a bomb to get to work in this time as they had no loan car.