[old_master]

It depends on how good of a job you want to do. If the system is empty, the accumulator has been exposed to humidity and the desicant inside is saturated. The only fix is to replace the accumulator. As a precaution, the fixed orifice tube should also be replaced. Make sure the compressor has the correct amount of the correct oil in it. Evacuate the system for a minimum of one hour, then partial charge with R134a refrigerant and leak test the system. If no leaks, finish the charge. That is the proper way to do it however, it's your vehicle and you can replace just the compressor and recharge if you like.