If you have no cooling due to the evaporator problem you also need recharging as leaking is the problem.
A good leak check is the answer to your question. I recommend you find a good independent that uses flourescent oil additives and ultraviolet testing for the surest answer. You will find the day-glow answer all over the transmission if the evap is the answer. The dye is carried out the water drains over the trans. It is an exact diagnosis. Electronic leak detectors, although the only way approved by MB, are very poor for evaluating evaporators. All A/C specialty shops do it that way now and even some of the manufacturers are installing the dye at the factory (not MB though)
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician