I can't help with recommendations on speakers or an amp. But for the dash speakers, you might look at the adapter rings on eBay for $50 so that you don't have to modify your speaker grills to accept new speakers.
Sunset Imports has the rear speaker kit for $130, and they you can upgrade the speakers if you want.
If you don't mind not having an OEM setup an audio shop could install door speakers fairly easily, but if you want it to be OEM you will have to replace the door panels which could cost a few hundred dollars.
-Rick
