I once attempted to change the brake fluid... I ordered this thing called E-Z Bleed ($40), a device you need to bleed each individual caliper. I got the system... and the brake fluid (Mercedes-Benz), and went to work... I couldn't do it! I didn't want to take any risks because if you get air into the system that can be a real problem.
To make a long story short, I would let your mechanic do it. It only cost me $40 at a Mercedes dealer! Hate to discourage you, but unless you really know what you are doing, I would not do the brake fluid or trans fluid. Other than that... you can do most basic maintenance yourself.

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2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)