I seem to remember that they have to remove the front bumper on the Caravan to install the cooler.
You can find a good B&M or Hayden "Stacked plate" trans cooler for around $75 on eBay. This is just an example that I came up with quickly. Best to do your own research.
http://cgi.ebay.com/ebaymotors/Hayde...Q5fAccessories
For a few extra $ you can get a pusher fan like this one (if there is enough room for it):
http://cgi.ebay.com/ebaymotors/PROCO...Q5fAccessories
You will end up with something like this:
Try to stay away from the cheap "Pipe & fin" type oil coolers. They work but are much less effective for the same size cooler. Like this one:
http://cgi.ebay.com/ebaymotors/Deral...Q5fAccessories