WOW, You are takingon a big job for a do-it-yourselfer, but I'm quite sure your up to the task. The exp. valve is located inside of the car below the dash in the driver's area. To access it you will need to drop the lower dash panel off and lay upside down on the floor. I would have used a new compressor for they are the same as on many GM cars and trucks and are cheap. The conversion is straight forward, be sure to get all of the old oil out of the system using a product such as BG FRIGI-FLUSH. Then install a PAG or equiv. oil. The new expansion valve and drier should work fine. BE SURE TO CHECK THE AUX FAN(S) FOR PROPER OPERATION.
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM