speakers should be easy, find out what size the stock f150's are and fit those or else cut out your door panels to fit 6.5"
A lot 'high schoolers' just put in huge subs by off brand companies that sound like crap. If you wanna do it right, upgrade your deck first, then your component speakers and amp those. After that is done and you have quality, add the bottom end and get some subs. If you're looking for a decent setup, I'd expect about $700 or so.