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.