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I would check to see if your compressor is getting power when it stops cooling, if it doesn't then start troubleshooting the circuit. This is not too difficult but you cannot guess when doing this kind of work, you'll end up replacing incorrect parts. Better if you diagnose first or have a shop diagnose it for you. You looking at paying at least 1 hour diagnosis time to check it out.
They are normally in a housing where the upper radiator hose attaches to the cylinder head. You might find a picture if you look on parts.com or one of the other parts sites.
Look at this site: http://www.instantestimator.com/ or go to a body shop and they'll give you a free estimate
We've seen this quite often on many different types of vehicles, and before we make any repairs, we ask that you put a bottle of Chevron Techron Plus Additive in a full tank of fuel and drive it. Often times the fuel level sensor gets a film of contamination from the fuel, and this is the only additive I've seen that actually cleans the sensor. It's a cheap fix too, and even if it doesn't work, it still helps to clean other parts in the fuel system (injectors, valves) It has to be this exact type: http://www.chevron.com/products/prodserv/additives/tcp.aspx Good Luck, hope it works for you!
When does it overheat? Is the cooling fan operating properly?
You'll need to pull the center console out to see what has been damaged. You should take this to a Mercedes shop and get it looked at.
This is quite an abnormal condition, so it's hard to know exactly why this is happening, but if it occurred after an oil change where too much oil was added, then you have a pretty good case against them. Has the pump been found as the problem? How long after the oil change did you notice it was overfilled and when did the pump fail?
100,000 miles is quite a long time between changes, at my shop we suggest it every 40,000 - 60,000 miles, depending on what type of driving you do and the condition of the fluid. I would verify that you have the correct fluid type, correct fluid level and that the filter is not plugged. Did you install a new filter?
Check out this article, it may help: http://repairpal.com/gm-4wd-warning-light-issues
The hood is probably frozen closed. Try tapping around the edges of the hood to break it free, or maybe some warm water around the edges. I have this happen when I'm up in the mountains, and these things normally work.