P0170 is commonly the Mass air flow sensor but this part is not cheap so check the others things first as MB DOC suggests. You can save some money by just buying the insert rather than the whole thing but some have had problems trying this. IIRC you'll need torx bit to get it off. You can see what the entire thing looks like at FastLane or get an insert from ebay.

You really can't just add ATF with the 722.6 tranny. The correct level is important. You'll need to buy a measuring dipstick. You'll also need special MBZ fluid. Car needs to be at operating temp. Carefully remove anti-tamper clip from cap. Add fluid until you get to the correct level on the dip stick. Add slowly unless you have an easy way to take out extra fluid like a Topsider oil vacumn.

glenmore
1991 300CE
2000 C280