Crazy Gauge Voyager Problem

Hello,I'm new to this board ,this is my first post.I'm in the process of buying a 1998 Plymouth Voyager with 55K on the clock.Getting it from a dealer friend of mine in PA.Only thing wrong with it is the "gauge" problem which seems to have been well discussed on this board.My question is can someone post a definitive ,step by step fix for this problem? In other words ,first try the battery clean up fix then go to the IOD fix etc.,etc. Also how many of you here have had success with changing the Body Module.Did it solve the problem?It's too expensive a part to be replacing it only to still have the same problem.

Thanks in advance,keep up the great work!!

Gary Y from Staten Island,NY