Learn to improvise on the piano

I’ve been playing the piano since I was five. I started out playing by ear and begging my parents for a piano…and even begging the neighbors if I could play THEIR piano.
I learned to read music and now I can’t really play anything without it. I want to learn to read chord charts and to play from fake books. I also want to learn to play great-sounding arrangements from bare-bones sheet music. Jazz it up, play alternate styles, use substitution chords, and sound professional.
There are lots of books out there, and I found some DVDs available online, but they are REALLY expensive! Especially for someone with my budget.
First, I need to find something to get me started.
I may also call the area colleges to see if I could talk to a piano teacher and see what they might recommend.