Can you link to the TPS that you ordered? I ask because from the research I've done, you can't replace just the TPS. The TPS is part of the throttle body. You have to replace the entire throttle body. And if you end up going that route, you might aswell upgrade to the 74mm throttle body. It's one of the most common upgrades on the forum. I ended up purchasing a used mercedes throttle body for $40 + $20 shipping. I had plans to try and swap it out myself using this guide here. But I ended up letting my mechanic do it while I already had it in the shop. Cost me $130 labor to have it swapped out. Should have done it myself, but ah well, it is done now.

If you end up needing it:
74mm TB upgrade guide - Make sure it says 113 141 0125 on it
74mm TB
http://www.ebay.com/itm/98-10-MERCEDES-MASS-AIR-FLOW-SENSOR-METER-MAF-S500-S430-1130940048-0280217810-/300854699060?pt=Motors_Car_Truck_Parts_Accessories&hash=item460c566434&vxp=mtrhttp://www.ebay.com/itm/Mercedes-Benz-W202-W203-W204-NEW-GENUINE-Throttle-Housing-O-Ring-305-997-03-45-/151161574603?pt=Motors_Car_Truck_Parts_Accessories&hash=item2331ee94cb&vxp=mtr