If you are completely new to car audio I would take 2 steps back and relax. You have some knowledge to gain.
1. with the right tool it is not hard, there is a panel tool at your local auto store get one their like 8 bucks.
2.There is 5 1/4 in the door "as far as I know" different speakers have different mounting depends as well.
3.For there that is were I would install your tweeter in the component set.
4.The components are much nice and are just a tad more difficult to run but not much definitely worth the extra time. If you are going to go with a nice set of with hertz or image dynamics infinitys have very harsh tweeters.
5.You can use the factory wiring in the doors just have to make sure that you use them before the factory crossover.
6.Dynamat or fat mat I have used both and prefer dynamat just dose not have a smell to it either.
7.Take your time and do it right make sure that you have the wiring harness for you z as well. Also the ground wire has to be grounded get you some self taping screws. Or right were the shift knob is there are bols loosen one us and slide a U connector there for your ground.
8.I am against rear fill you do not need it and it makes the music not sound right. Just get a nice set of fronts you will be much happier.
9.If you need any help or more guidance contact me weather it be a PM or threw instant messenger aim and yahoo are reimermatt. Take care!!
Here is some more info that might be some help to you
Car Audio 101