OK... seeing as you wont listen to me on MSN, it'll be here.
I replaced the 2nd & 3rd bulk rings in that box as well as new bearings.
You WILL NOT have to replace all of them - only the 1st gear bulk ring.
It was in good serviceable condition & I did not see reason to replace it.
Obviously your different driving style (to me) nessatates it to be renewed...
It's NOT a job for you to do - you need to find someone who's familier with Zed gearbox's to do it.