HBguy

I shopped around for a shop to do the transmission and differential fluid, and was getting a little frustrated with the local 'Benz' "specialists" that all gave me different reasons to not trust them 100%. I gave up and decided to do it myself and bought both a 14mm socket and also a key on amazon for about $24 for both. It was as easy as you could imagine. My tip is to do it yourself if you can get the car elevated (I used regular jack stands) and my hint would be to buy both the key and socket for the 14mm hex because it could be tight to get in there and also it could be locked on tight and a hard turn.

I know its not a traditional 'DIY' with photos but there's threads on that. As usual, make sure you take the fop one off first so you know you can fill it if you drain it. I used
Valvoline SynPower SAE 75W-90 Full Synthetic Gear Oil 1 QT , with the best price from amazon.com.

HBguy

One of the shops even told me they didn't have the tools to do it, but had a W108 in their websites photo. Shops nowadays just want the OBDII to give them a list of parts to change. Repairs and service is a thing of the past.