Larry...I am also in the process of trying to replace my tensioner (and idler pulley since something is squeaking and I figured it was one of the pulley bearings). It wasn't in my Chilton manual and hoped to find the answer on this site.
Here is what I found on WikiAnswers: (it isn't overly helpful but it sounds like you access it from the bottom w/ a 15 MM socket...althought I doubt 2 - 3" extensions is possible...)
How do you replace the Serpentine Belt Tensioner on a 1998 Dodge Caravan?
I have a grand caravan, with a 3.8l engine.
The s-belt slipped off on my way to work, and I went to put pressure on the tensioner, and the bolt snapped in half.
I drove the van up on ramps, and was able to access the 15mm nut on the back of the tensioner. I went to O'Riley auto parts and they showed me the replacment, and then it was a snap. I used a 3/8" ratchet with the 15mm socket and two 3" extensions. It came right off, and the other one went on easily. I had a 2x2 piece of wood that I used to help hold the tensioner in place, while I worked from the back side.