1985 Maxima - needs help!!

I recently acquired a 1985 Maxima 5 speed for a good price (free) from a family member, but there are some problems I need fixed. First, only 1/4 of the fuse box seems to be getting power. Also, I have no power to the lights, security systems, radio, cooling fans etc. The car will start but that is about it. I am having it checked at a dealer and if the fix is relativly cheap, I will keep it, otherwise I will donate it and get the tax writeoff. Does anyone have an idea as to what is the problem with the electrical system??? I would hate to lose it because I drove it when it was running and it was a jet. It does not look like much, but I figured it would be a good second car.