Hey Terry,
While I've never done the inner seals on a TJ or Chrysler era Jeep, I did take a quick look at the Spicer/Dana book and they appear to be similiar to the pre 86' D30/44. In which case yes, I would replace both as your going to reach through the opposite side seal to seat the other (or atleast one side anyway) and since it's like a $5 part, why not? For my AMC era Dana's, I use National Oil Seal Brand, but I sure there are "better" aftermarket parts that you'll pay more for.
Again, assuming theres has been no major engineering breakthrough in the past 30 years between the two different generations of axles, its not as straight forward as the book is telling you and no you don't really need the Chrysler tool. You will need to remove both sides of the axles from the housing and remove the carrier as well. Once these are out of the way, each seal will pry out (inward towards the center of the diff housing). They go back in similiarly, you'll start one side into it's seat with your fingers and then drive it from the opposite side with a long tool that reaches in from the outside, down the axle tube. For the ones I've done, I found a piece of 1.5 PVC pipe is the same inside dia. of the seal. I just adp'd a broom handle as the driver rod. I've read that you can also use a deep well socket and extensions too? There is a photo of me replacing one of these with the tool I made in the Tech section (Dana 30 Rebuild).
The process is not hard, but time consuming. Again, thats providing we are talking about the same things.
