lucegunz

Honestly to answer your memory question, most laptop memory sticks are not compliant with desktop boards... like the one you listed, yes even though that intel board is super tiny its considered a desktop board.... so i dont think youll be able to use any of the ram sticks you but ram is cheap 15-20 bucks will get you a one gig stick for that board....

my carputer buying all the parts from scratch, which it sounds like you already have a good harddrive, cost me under 300 bucks that includes a small case (which included most of the cables needed and the mother board has a few too bundeled in) it included dc to dc power supply so i can draw power directly from the battery etc... basically the whole system cost me around 275 USD...

As far as the radio goes i know certain screens come with built in FM tuners so you dont need to keep your head unit and there are other alternatives i belive but i did not have to explore those routes as my screen included AM FM radio tunner....

EDIT: THough my screen was very very expensive i think you can find one that will keep you under the 700 budget you listed no problem....