as far as the location of the leak, it could be any number of places.

the most common leaks on these cars occur at the compressor, hose connections, and occasionally at the evaporator core.

less common leaks are from the condensor or actual hoses them-selves.

the only real way to find it is going to be usind a dye, letting the refrigerant work its way through for a bit, and then looking for traces of the leak with a sniffer and some u.v. lighting.

a cost estimate is hard to figure. for a simple re-charge and dye, you can expect to pay between $50 and $130 depending on which part of the country you live in. For finding the leak and then repairing it the cost will be based on how long it takes and what parts are faulty.

i am an advocate of fixing problems but realistically, if the car is cooling somewhat still that means that not much has leaked out, maybe .5lb and if the car has never been re-charged that means you are looking at spending around a hundered dollars every six years to keep the a/c working. it may be cheaper to just charged it and not worry about it until the problem returns. At that point it should be fairly easy to find the problem due to the dye.