This is a pretty generic answer, but it should address your questions properly:

You want to get components for your front doors - no one makes them in 5 1/2" sizes - they will be either 5.25, 6.5, or 7". Generally a honda is 6.5"s

If you buy what are called components, you will receive three items typically, the midbass, the tweeter and a crossover. The crossover is called a passive crossover - it's typically not very adjustable, but it's effective and saves you from adding additional channels of amplification.

Put the midbass in teh factoyr location and the tweeter where you like.

As for the fiberglass question.....that is totally, and 100% wrong. An enclosure with NO parallel sides is actually ideal. It's actually nice to have angles in the enclosure so that the back wave doesn't actually come back and hit the back of the cone.

So glass as much as you want, you are ok there - just make sure the glass is curved, there are no air leaks, and it's thick enough so that it won't flex.