Bought a D2 back in June that had sat for 3 years and after getting it running again one of the first things I noticed was that the brakes hardly work. The pedal is extremely hard to depress and when it is depressed the vehicle slows down but barely. What should I look at first?

 

Brake booster, or the vacuum lines going to it. Changing the booster is an hour or so job (including bleeding the lines), pretty simple.