^^^^^
Yep if its the same as mine (2005 model) the ceiling is pretty thin ply with a white paper finish on it that does not like getting wet. First thing is to fix the leak and then you can either remove and replace the ceiling or just sheet over the top of the old ceiling. I sheeted over the top of mine but did remove enough of the damaged section to check the roof structure, there was no real rot but the staples holding the timber together had rusted through in some points. If the ceiling is till flat the structure should be ok but if it is starting to sag in the middle there maybe more than cosmetic issues.
Cheers,
Jay