Jeff,

I changed the transmission oil on my 99 ML 320 at 75k miles. It's definitely a DIY job, at least on mine since I could drain the torque converter too. Even if you can not drain your torque converter you can measure what you take out from the pan and put in the same amount. Just measure the old fluid when it's cold and the fluid you put in when it's cold too.

You need a new pan gasket, filter, sealing washer for pan drain, sealing washer for torque converter drain and of course 8 liters of MB synthetic transmission oil (part# A001189210310)

First drain fluid from transmission thru pan, then from torque converter. To find the allen heand drain plug on the converter turn crank from front of car (27mm socket) until you see it.

Owners manual says capacity for my vehicle is 7.5 liters. I measured what I draind out and it was very very close to 7.5 liters. I figured if I put in the same amount I took out I could do no harm. I let it drain out overnight to make sure I got as much out as possible. I must say the condition of the fluid seemed quite good.

Install filter, gasket, pan and drain plugs with new sealing washers and fill. I put in as much as I could with the engine off, then turned it on to fill the rest. I put in exactly 7.5 liters of fluid. No problem.

To check it I took it to my friends shop, where they work on Mercedes only. He has the special dipstick which I think he said is used on some of the other models of MB too. Anyway it's just a dipstick with some marks on the bottom. One for when the fluid is hot and one for when it 's cold. I saw this dipstick tool for sale on some tool website for around $25. We checked my car and it was in the correct range. He then put on one of those little red tabs that holds the filler cap on to make it official.

That's it. You've just saved a bunch of cash.