Add a torque wrench and you need torque spec. On my 94 E320 the pan bolt spec is 8NM, I think. Any body know spec on a 2000 E320?
Use a lintless cloth to clean pan. Pan must be clean clean clean. Some use a chammis (spelling?), you know lambs skin. But I tried a few different rags, until I found an old sweatshirt that did not leave ANY lint.
Also, I recommend cleaning the threads of the bolts with a wire brush. Just enough to wipe away the corrosion. The bolt will go back in much smoother.