3d scanning is in it's infancy.
It's not good with holes or voids in objects and the cheapest desktop model that's worth having is over $1000. The einscan: http://3dprintboard.com/forumdisplay...n-S-3D-scanner
The 'affordable' (their term, not mine :-) industrial units start at around the $10-20,000 mark.

By the time you scanned a part and spent a couple days tidying up the point cloud and adding all the details the scanner missed, you'll probably find that it's easier to do it yourself.

One of the things that keeps cropping up from our american members is how hot it gets in your cars. Not an issue in the uk.
So you'll need to be using pet-g, which is a good mechanical plastic with a higher softening point than abs or pla.

There are also some pla's around that you cook after printing, they shrink slightly, but get stronger and a lot more heat resistant. Up past the 100c mark, apparently.

I've made and replaced plenty of household items, and can't see any issues with plastic car parts - but probably best to avoid engine parts.

So yes it's doable, but you will need to do most of it yourself :-)