I just went through the same process on my LS, Spiegler brake conversion, and their braided stainless brake lines .
Haven't ridden the bike yet, but the materials and craftsmanship have the appearance to being of great quality .
They are rebuildable, if something wears out .
I also got the kits to do both calipers, and master cylinder rebuild from Motobins, and I would recommend them if you are going to do this job to your bike .
If you do work on the calipers. either the Brembo, or ATE, the small o-ring that goes between the caliper halves, is not available from BMW, just be aware of this before you take them apart .
The round rubber part, sounds like the plug that goes into the ends of the centerstand .
If the rear brake shoes, aren't oil contaminated, I'd just rough them up a bit with sandpaper to get rid of any glazed areas, and reinstall them .