With the rear squealing, you may need to replace the axle spindle end too.
Your Disco1 axle will have 2 seals on each axle end, a small one (inner) and a larger exterior one. The larger one is available in a double lip version, that's the one to replace it with.
The small one is to keep the diff oil out of the bearings and the large one is to keep the bearing grease in the hub.
Some guys only run the outer seal (large Dbl. lip) and allow the diff oil to lube the bearings in the hub (2 sets of bearings).