Now I've seen it all...

There's a great novel (Cliffard D. Simak's A Choice of Gods) on that subject. Yes, if something happens, we will lose the technology we've gained - but what effect would that really have on us. Necessity is the mother of invention. If we are suddenly without vehicles because there is no one capable of fixing them, we will learn new ways (or old) to get around that).

To me, most technology (other than medical advances) has simply made life more convenient - it hasn't changed the way we live. If I couldn't figure out how to fix my car, I'd walk, ride a bike, etc. All a car has done is make it faster to get from point A to point B.