Faulty MLI?

I apologize for my ignorance, but..

The emissions workshop messages pops up sometimes and is accompanied by the yellow multi-light indicator...how long should you go before gettting it checked out? there have been some false indicators in the past and i don't know if it is just a malfunction or if my car is going to blow up at any time. heh. Something always seems to be wrong with this stupid car.. Does anyone else have such a problematic jetta? Also, my front bumper (spoiler?) thingy is semi-broken from scraping the curb...any idea how much one would cost?

Thanks. :)