The m104 is a bit tricky but, doable by a DIYer given they have some mechanical knowledge. The worst of it is the mounting bolts and getting it out of the hole.
Diff seals will leak on occasion, also not too hard of a job except for the axwardness and weight of the diff.
Project Smoker, '87 603 powered wagon
Hauler, 96 CTD can you say torque?
Toy 73 Cougar xr7 convertible
Acme Automotive Inc.