Transmission Fluid Flash???

I have a 2000 Jeep Cherokee Sport with 78,000 miles... I am seeking advice as to whether or not I should replace all of the transmission fluid (my best friend manages a Jiffy Lube, so he does it personally and at a discount!). I have never replaced all of the trans fluid, but have kept up with the maintenance schedule for "regular" trans fluid changes.I know little about auto maintenance. However, I have come across differning opinions as to whether I should do this or not. Any advice will be definitely appreciated!

Thanks.....

Yes, if your friend works at Jiffy, then you have a nice "hook-up". I would recommend changing ALL the fluid at this point. I too have a 00 XJ and have changed the fluid regularly, twice completely. At 86k no problems a all, in fact still thinking of going to a full synthetic fluid, due to milage and the fun I have with it.