I have a 78 Scottsdale k20. The brake light came on and then a couple weeks later the brakes went out. I only drive it a little on the weekends. Probably drove less than 20 miles with the light. With the truck running, the brake pedal will push full travel with almost no resistance till the last inch. The pedal comes back up very slowly. I can't pump the brakes up. The emergency/parking brake also does not work. The break fluid reservoir is about half full. I would appreciate any help. Also, any suggestions on resources to learn about the mechanics of this truck like books or other websights?