8 3/4 rear seals

Probably a noob question but are there 2 seals in the end of the diff tube? I have the axle seal fitted but how do the rear bearings get lubricated and how do I stop the oil from coming out onto the backing plates...I googled some pics but Im still not clear...seen some gaskets for the plates the hold the axles in..are these critical? The reason I ask is I did a diff centre swap and now both sides are leaking badly...it wasnt before I did this and the mess and smell is driving me crazy