How do you check the transmission fluid level on a Mercedes Benz 1999 e320?

Dealer will have to. No stick. Supose to have a lifetime "sealed" system. If something does happen, dealer has a special pump /with fitting that suck the fluid out. They replace exzactly to spec's. Personally, owning a 1998 E class I don't think much of this system. You can get the dealer to do a fluid exchange around $230.00. I had it done when my car reached 100,000. Answer 2: I was a Mercedes mechanic. I bought a dipstick from the dealer. I service my transmission every 30,000 miles, changing the oil & filter and draining the torque converter. After draining the oil, the pan can be dropped by unbolting it (under the car) so the filter can be replaced- including a new pan gasket. Torque converter is rotated by hand with a big screwdriver so the little drain plug can be removed and replaced. Fluid from the dealer is not cheap but worth it.