Cummins Diesel techs/ rear seal leaking have question..

I have an 06 dodge 2500 with a cummins and I happened to crawl underneath the truck and noticed some seepage from in between the tranny and engine. Took it to the Dodge dealer and they told me it was the rear seal on the engine. Is this an issue with these engines. How involved is the replacement of the seal. Just looking for some advice or feedback. Thanks.

you have to pull the trans , do you have over 100k on the truck ? should be a warranty item ???