Fuel Gauge Broken ?! :(

Hello there. I am new to this forum.
Recently, I filled up my tank and when I got back in the car I noticed that it was still on empty. Over the next few days it would fluctuate from being stuck on full, to ending up in the middle somewhere. Whatever the case, everytime I turn my car off and then on again it changes, and then stays the same throughout the drive.
I have been told that the fuse is probably good since the gauge seems to work irratically, and that I probably need a new "Sending Unit" which is mounted on the gas tank itself.
My question is twofold:
Is the diagnosis correct?
Does anyone know the overall steps involved in replacing a sending unit? i.e. how to access it, on a scale of 1-5, 5 being the hardest, how hard of a job is it.
I am pretty good at doing most maintenance things, brakes, tune ups, etc. I am just trying to gauge whether or not I want to tackle this one myself or not.

Thanks,

The fuel level sending units are a Easy job IF

 

You have the Factory tools to drain the fuel tank and to remove the sending units..they are accessed from under the car

sounds like a wireing fault to me. i recomend that before you do anything you replace the fuse. embrking on jobs like that sound simple but really arnet. so just replace the fuse and mayby check that the wireing connectors on the sender unit are firm.

Actually, Mercedes has admitted that the full gauge problem is evident in many of the '01 C240's... if your car is under warranty, they'll fix it. However, it's been two times back at the the shop for me... for the same issue - and it's doing it again...

I've had that problem too with my 2001 CLK430, it was fixed under warranty

yes take it back to the shop because it's the sending unit in the tank.  Unfortunately this is a very common problem that doesn't appear to be getting fixed for very long after a new one is installed.  Hopefully mercedes will build a better "mousetrap" and come up with a permanent fix for these faulty sending units.