Make sure all the components are installed, and the gas is good quality. The price seems too low, so I suspect dealer is making some compromises. Relays, Automatics switches, and fan in front of AC-grill are sometimes missed out.
I got one installed in my Datsun 120-Y from Tariq Road (Back Lanes) in Rs 19000 from someone I knew, otherwise price is usually 20,000. Had to install a shroud over the radiator fan next day, cost additional 700.
Later on 1-2 days, the person I knew detected a leak in the pipes and cheap quality of chinese gas, so he sent me back and got everything replaced for free. I would never have known about these things myself.
There is a new korean/taiwan brand, forgetting the name, it is good quality and uses the newer gas (the old gas,R-22, is hazardous and is being phased out).
Where do you live? My contact is in North Nazimabad (Hyderi Thaana) and he gets the installation done from Tariq Road. He really makes sure everything is genuine and installation is perfect. If you are interested, call me @03003279347 (Wahaj).