1997 Dodge Caravan Gauges on Dash

Electrical problem
1997 Dodge Caravan 6 cyl Wheel Drive Type unknown Automatic 160000 miles

Hello I was recently looking into buying a Dodge Caravan.
The vehicle runs great. The only thing thats wrong is that the speedometer and the gas gauge and the odometer don't work. The windshield wipers work but they wont stay on, they cut off and cut on. The guy said the vehicle sat for about a year and he drove it off and on. He also said that when he bought the vehicle that all of this stuff worked. We also had to jump the vehicle when I went to look at it if that plays a role. I was just wondering if you could tell me the steps in which I should take to figure out why these things don't
work and how I can get them working again. Thanx