This is embarassing, but my husband is in Afghanistan for a year and I picked up our C280 yesterday at the factory, and I'm unsure about how to drive it.
There is a C(comfort) and S(sport) mode to drive it, but I don't know what the difference is. The person at the factory didn't explain it very well. The book said to drive in C mode for the first 1000 miles, but the factory rep did not say that. What do I do?

C mode starts the car off in second gear and causes the transmission to shift more smoothly. Off the line acceleration will not be as brisk in this mode, but shifts will not be as noticable. S mode starts you in first and cause the trans to shift more succinctly.
The recommendation for using C during break in is mostly because it encourages less spirited driving (which is key during the first 1000 miles).

You can leave it in C or W mode, shouldn't cause any problems, even after the break-in period. You will find that the C mode has smoother gearchanges as it upshifts at lower rpms.