Help, not shifting past 1st gear?

Hmm, your 2006 with only 56,000 miles? I'm not sure it's the transmission, it could be either a computer, speed sensor problem or some other electronic malfunction. Bring it to an independent Mercedes Benz garage and have them run a diagnostic code. I imagine that you have AAA roadside services? I doubt it's the transmission.

No money and "Mercedes" don't go together-

I can't believe that Kim has "no money ", just a figure of speech. You can't drive any car with "no money ".

The transmission has a life support system. If the fluid gets low, (Yes you can have a leak) it will not shift out of first gear. This is to save the transmission, and allow you to limp to a garage. If you can, check the fluid level, or have someone with knowledge on how to check the fluid level do it. I believe the car has to be running to do this check. If it is low, have it serviced or fluid added. My wife's 2002 with 24,000 miles on it did develop a leak due to lack of constant driving before we bought it. Seals do dry out then when heat and pressure is applied, it will develop a leak. Budgeting can save money, and what was paid for yesterday does not mean it can be afforded today. So no judgement on the lack of funds from this guy. Adding fluid can be a temp fix, but put away money to have it serviced soon. Independent garages can be a lot less expensive than a dealership for needed repairs. Finding a good one that will work with you is the challenge. I have a great garage here in Orange County Ca. if you live close to here.

you have to have it diagnosed.on 2006 models give your vin to the dealer and ask transmission type if its 722.9 the computer is inside the transmission and mercedes does not sell the part.You need to talk to a shop who specializes on mercedes and c if they can get the part.if not you are looking at $ 1200.00 at the dealer.If the earlier version it might be the computer itself or circut board inside trans.good luck