The you have nothing to fear. You should take action and send your letter of demand.
If they then threaten you take out an AVO to make sure that they do not approach you and report this to the police.
You cannot let your fears of possible actions affect what you want to do.
Get the police report as evidence of their findings and then you can use this to sue for the costs of the repairs to your vehicle.
The process for suing them is set out in the following link
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