I personally will not replace parts that are not bad. If one of the dog bones is bad you will see pieces of rubber poking out of it.

Same goes for the differential mounts. You can shake the third member and tell if they are loose. These are the most common problem when feeling rear end looseness.

Check everything before you get under to do the job and have parts on hand. Replacing EVERYTHING will sometimes result in more problems than you started with.

If it ain't broke, don't fix it.