Bob,
Sorry about your reverse gear problem. I assume the plates that were broken are the clutch plates. If so that seems to be a common problem with this drive a ZF45A modified for the D3 by Volvo. The ZF dealer that obtained a new drive for me thinks that the Volvo torsional interface bolted to the engine flywheel may be our problem. I am beginning to think so also with all the drive failures reported on this web site. Other engine manufactures have had similar problems with this drive and found out that their torsional interface was insufficient. I tried to address that with Volvo and they indicated the interface was adequate and directed me to ZF for help. However if you read the warranty on the ZF drive it is the engine manufacturer’s responsibility to provide a proper interface.
I did not have a warranty so I cannot help you with that, however if yours is not going to be covered by Volvo, I would find a ZF dealer and purchase a ZF45A for under $2K and have them take the Volvo shift block on the gear that failed and replace the manual shift block in the new ZF. You now have VP gear compatible with your D3. Also, since you had parts break in the gear, some may have gotten into the oil cooler. Since the VP oil cooler is not cleanable I would purchase a new oil cooler. If you go with Volvo it is $450 or another manufacturer less than half that.
Good luck with the repair and $ from Volvo.