I own a few Chrysler Crossfires which are really SLK320s underneath. A Chrysler exec told me that Mercedes Benz required belly pans on all their vehicles because owners do not "want to see oil drips on the pavement under their expensive cars". It's kind of a German thing. Obviously, if you're leaking oil you have bigger problems than a missing piece of plastic.

Unless your old one was totally destroyed, you can probably find some similar heavy plastic (rubber?) and patch it. When I bought my car there was a patch that the previous owner cobbled together with pop rivets. Not pretty, but no one sees it and it has lasted for 90k miles.

 

Seems this issue came up a while back in another thread. I remember one post where the guy said that he was driving at fairly high speed on the highway without the plastic pan, and could feel the front end getting light the faster he went. Point is that I think these pans serve a useful aerodynamic function which shouldn't be overlooked. Anyone?

 

^^^ yeah it's deffinately a 'useful function' but one could argue that its not necesarily important... IMO get a new one of fix it!