The general consensus is that, while it's possible to retro-fit air conditioning to a car, it's really far more expense and hassle than it's worth. Better by far to simply trade your car in for a similar one that had air conditioning fitted at the factory. There will be a cost of change involved but it will probably work out cheaper overall than a retro-fit. Besides, retro-fit will end up costing you more at resale time as many buyers are reluctant to buy a car that has been modified, even if by a professional company.