You're buying an expensive car, so...
1. Find some reputable performance workshops nearby the the cars location, call them up and ask if they'd do a pre-purchase inspection for you.
2. Ask the seller if you can take the car for a pre-purchase inspection, if they say no. Walk away, it's not the car you want.
3. FLY up there, we're not talking about a $3000 R32 GTST, spend $500 on a weekend trip to go see the car in person... Drive it, get the pre purchase inspection done.
4. Once happy, go into your bank and get a bank cheque drawn up (make sure they're open on the days your planning on buying)
5. Make sure all the paperwork is in order before you leave, you don't want to be missing an interstate signature.
6. Deliver the car yourself to the car transport place. Taking plenty of pictures of the car out the front of the facility, to prove any damage that could be caused.
7. Hire security guards if it is going to be travelling through NSW at all... I hear they've got a problem with non-34R owners getting jealous.