I definately recommend the fluid change.I have seen too many problems with these tranny's and the fluid always seems pretty bad when the get about 60k or more on them.It's an expensive service,but well worth it.
You can set the fluid level pretty accurately without the mercedes diagnostic equipment.
With the trans empty, add 4 qts or liters.
Start the engine.Add 2 more qts.
Let the engine idle to operating temperature.
Thats the point when you start checking and adding fluid .
You will need the MB dipstick. (Part # 140 589 15 21)
Your crank bolt is a 17 mm allen.
Mercedes Benz Master Tech
ASE Master Technician
Owner of "Behind the Star Inc."