4x4's and tax?

Howdy, I have a 100 series that is currently both commercially registered and insured. I have used this vehicle for work and claimed all expenses for tax purposes as I have been self empoyed.

I now have a new job which amongst other benefits provides me with a company car with private use included, so my trusty 100 series now resides out in the back shed gathering cobwebs.

My question is what is involved in transferring it back to so called 'private' usage in the eyes of the ATO? For the time being I would like to keep the 100 series for camping trips as it has $15K worth of well sorted goodies on it and is in A1 condition, but what are the ramifications if I do sell it later on when I get that 4x4 auto TD company car I'm angling for? Do I still get a whopping tax bill on the discrepency between the actual selling and depreciated price, and also do I have to pay GST calculated on the purchase price of the Cruiser, or is the now 'privately' owned vehicle exempt and treated just as any other private car?

Naturally I will be seeing my accountant about this matter, but thought there might be someone out there who has some practical knowledge or advice about this kind of thing. I want to get the structure on place before the end of financial year for obvious reasons.

Does anyone else who has a company car have any advice in general? Have you kept your own vehicle or do you just use the company one?

Thanks in advance.