I'm quite sure "guru" isn't quite appropriate. I've just made a hobby of failed final drives. There are professional mechanics and mechanical engineers who understand bearings and gearboxes much better that I do. I am just persistent.
I'm with Frank, I don't trust dealerships, sorry that the good ones get painted with the same brush of suspicion as the bad ones, but I have heard way too many "blow smoke".
I am happy to cut open another bearing, but don't think I'll learn much from that one. I have a box full of trashed bearings in all stages of degradation. The reason I wanted to see Franks was because of the stage of failure when he opened the drive. He caught it early based on wheel rotation roughness, the retainer was broken but that wasn't identified until the drive was opened. I also have seen drives where roughness was felt but the retainer was still intact. This has helped me get an understanding of how the bearings are failing.
The bearing pic'd in this thread is pretty typical. I am sure the races will have severe spalling. I am now out at the stage of looking to see the distribution of the spalling around the races, is it evenly distributed, or primarily in selected areas?
Cutting a bearing open with a metal cut off disk is pretty easy if you have the tools. If you want to mail me a bearing for cutting open and picture taking, I'm happy to do it, PM me for a mailing address.
Some metal on the drain plug is normal. A new drive will generate a fine grey paste that comes from the wear-in of the gears. The bearings shouldn't be generating anything and when they do, you are on your way to problems. The difficulty is knowing where the metal is coming from. All we have now is particle size, shiney big particles are bad, fine grey mud is okay. A good drive will generate the fine grey mud early in its life and then little to none should be generated as the drive "matures". At least that's my understanding of it at this point.
Wheel wobble is of no value in detecting crownwheel bearing failure. I have made this statement many times now but the wheel wobble test still gets talked about. If you have detectable play at the rear wheel, check your pivot bearings and swingarm bearings. Based on all I think I know about crownwheel bearing failures, you won't be able to detect play at the rear wheel because of a bearing failure until after the seal is torn, the oil has leaked out, and you have ridden another 5 to 20 miles. Then your wheel will wobble. Prior to that, your best indicator is shiney metal on the drain plug (yeah, hard to catch because it progresses pretty fast after it starts by most accounts). The next best indicator is roughness during wheel rotation.
Ari recently reported listening to his final drive with a mechanic's stethosope. That is a really good idea. The next best test is to feel for roughness during wheel rotation. I have suggested pushing brake pads away from the rotor so that the pads rubbing on the rotor isn't altering the sound or sensation of the wheel rotation. Those riders who have paid close attention to the feel of the bike have caught bearing failure early, prior to seal tearing and oil leak. Most riders discover the problem when the oil comes out. At that point you aren't going to ride very far, and you shouldn't as damage to other drive componets may occur. I've seen destroyed brake calipers and rotors resulting from riders trying to get further down the road after a drive failure. Not a good idea to keep riding IMO.