For some reason I've had to replace a water pump on my '95 4.0 about every two years.. Here's a link on how to:.. It's not too difficult, the first time it took about 4 hours, now it's about a 1.5 hour job.
http://www.autozone.com/servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/15/1d/85/0900823d80151d85.jsp