I would like to acept your advice, but I did say we are in Australia - Looking at the shipping details for the spare part, which I would have liked to order and try our luck at fixing it, does not allow for entering any overseas address - probably something to do with the tube of lubricant(?) as part of the spare gear set kit(?). Anyway, with things as they are, we are not in a position to accept your advice as relevant for our situation in Australia. Perhaps you can find a way around this? If so, we might be able to use a locally available lubricant, and have the spare parts shipped without any substances that upset shipping agents.
Anyway, pehaps you can assist. I shall click "accept" for your advice after clicking "Reply to Expert" assuming that options is stil available, hoping you will still respond and get back to us about the spare part (XXXXX@XXXXXX.XXX) in a way which will allow us to attempt repairs as you have suggested.