I did this R&R. I made many mistakes, and I now think what I did was likely unnecessary. For what it is worth:
1) While I suspected differential bearing whine, I thought that drive shaft bearing could be an issue. Why? 220,000 miles, and [mistake] I looked at the support bearing under the van without a good light. I saw light through and between the bracket and the bearing and jumped to the conclusion that the bearing had separated from its rubber support. Not so - If I had closely looked I would have seen that is the design.
2) I have edited ExpCourier's excellent write up with a safety heads up. Mistake - I did not chock the wheels all around and I had the van in PARK. In PARK, the drive train is loaded. When I dropped the drive shaft, the van moved. Put the van in NEUTRAL to start this project. In NEUTRAL, the driveshaft is unloaded and the transmission flange will rotate freely, making reinstallation easy.
3) I used crayon to mark the driveshaft at both ends and the middle. Mistake to use crayon, as most of the crayon rubbed off the driveshaft during handling. I should have used something to score the parts - a chisel or engraver. This became a big problem later as my front half of the drive shaft is missing the alignment arrow.
4) Mistake: I disconnected the support bearing, then front flange, then the rear flange. When the rear flange was disconnected, the rear part of the driveshaft dropped, the front half went up on the fulcrum of the safety bracket and killed the Espar pump to the left of the transmission. I should have had some support under the shaft to catch it when it dropped. It is not possible for one person to be at both ends at the same time and with tools in hand. Who knows what that pump part number is.
5) Note sure if a mistake or not. I rotated the support bearing to see if I felt anything. Nothing. But the bearing had horizontal movement that the replacement bearing did not. So I proceeded to R&R.
When I reassembled the driveshaft halves is when I noticed no alignment arrow. WTF. Alright, approximate with the crayon marks on the flange ends. Damn - rubbed off. Now I have a vibration around 55-60mph not previously there [thus not likely worn universals]. Only 20+ possible repositions to restore its balance.
On another note, the drive shaft support bearing has many suppliers. Most look identical. Further, it turns out that not only are there multiple Mercedes part numbers for it, the T1N seems to share the part with the Volkswagen LT. As for mine, I ordered a Lemforder. The unopened box had the part number I designated, but the identical looking part inside had a different number. Upon researching that number, it showed up as appropriate for the T1N,