Ok, repeated leaking at the front seal is indicative of pressure buildup due to restriction in the system - either the condenser or the expansion valve.
This is what your mechanic needs to do - refill refrigerant, have an ac manifold gage set hooked up that reads the pressures on both the high and the low side. Turn ac on and watch the gages. If high side pressure starts going up, then it is the condenser. If the low side pressure starts going up, then the expansion valve needs to be replaced.
On this model, it is usually the expansion valve that is sticking. It is a pain to do and about 6 hours labor as it is attached to the evaporator inside the hvac housing. The dash MUST come out in order to access it and replace it.
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