In this series of videos,
Part 1 - I am removing the wiper system (wiper arms, rain repellent, and wiper motor assembly in order to get to the Expansion Valve:
   • Mercedes W220 AC Service - Wiper Syst...  
Part 2 - This Part - Replacing the Expansion Valve
Part 3 - Replacing the Receiver Drier
Part 4 - Charging the system with Refrigerant (R134-a)
Part 5 - Installing the wiper system
I have done all the work on a 2000 S500 - but this applies to all other W220 cars such as S430 and S320. I have recorded the footage but editing is taking time. So, as I finish editing each part, I will be publishing them. At the end, I will probably have one last video that includes all the parts.

Nissens Technical Poster:
https://nissens.showpad.com/share/iXa...

You can do this job for little money compared to what a shop would charge (probably over $2,000. Here are the part and tools I have used:

Tools/Items Used:
AACM O.E.M. AC Expansion Valve P/N: 2308300184 - $21 - Autohausaz
ACM A/C Receiver Drier P/N: 2208300083 - $28 - Autohausaz
Santech A/C O-Ring Kit P/N: SH-227598634 - $27 - Autohausaz
R-134A Refrigrant - 3x12oz Cans (950g) - $36 from Autozone
A/C Manifold Guage Set - $40 from Amazon and others (may include can tap)
Hex Socket Set, Reverse Torx (E) Socket Set.Socket Extension Set, Light,
Towels, Wrenches, Torque Wrench, Gloves, Eyeglasses, Screwdrivers,
Scale, Needle Nose Pliers, Picks, R124a Can Tap,
Automotive Plastic Fastener Kit, 240 Pieces - $14 - Harbor Freight
Long reach Hose Grip Pliers - set of 3 - $15 - Harbor Freight
Trim And Molding Tool Set, 5 Piece - set of 5 - $6 - Harbor Freight
Wobble Socket Extension Set, 9 Piece - $15 - Harbor Freight
PAG 46 oil - 8oz - $12 - Advance Auto
VIVOHOME 110V 1/2 HP 5 CFM Dual Stage Rotary Vane HVAC Air Vacuum Pump with Oil Bottle - $129 - Amazon
Jack and jack stands or Ramps
Prices above are as of May 2023