Really depends on your D.I.Y level. If you can confidently change your eng oil, then you should be ok. It's not really complex at all, just follow my steps and take your time.

Things that will assist you;

# You will need to raise car using ramps or jack and stands, or use a hoist or pit if you have access to them.

# TOOLS you will need;
1) 5mm allen key 3/8" socket, for removing sump and convertor drain plugs.
2) 13mm 3/8" drive socket, 3/8 extension bar and 3/8 ratchet, for removing sump.
3) #2 phillips drive screwdriver, for removing filter.
4) 27mm 1/2" drive socket and bar, for turning the eng (clockwise) via the front crankshaft pully retaining bolt. (you will need to remove lower eng covers, held by 8mm hex head screws).
5) Large container to catch oil. (something that can hold about 10 litres).
6) Funnel for refilling trans.

# Make sure you use fluid that is mercedes approved, I use and recommend Dexron 111.
# Try to avoid over filling, If you do over fill you will need to drain via plug on sump. (If you take your time and add fluid in small increments this will be avoided).
# Be careful when removing drain plugs, as fluid will be hot, just as you should when changing eng oil, wear riggers gloves, long sleeved shirt and clear saftey glasses.

It may seem a bit daunting, but it's very straight forward and you can't really mess anything up, even if you have to buy a few tools. It will be far cheaper than paying a dealer and you will have great satisfaction knowing you did it yourself.