Just checking, you are kidding, right?
On a more serious note, I doubt the headgasket would be leaking, would probably be the valve cover gaskets, they always seem to leak on RB's lol.
Rear brake pads don't cost $300.
Its all pretty minor IMO, what makes him say it needs drive belts?
Edit: Do a full '100,000km' service and that will fix up the cam and crank seals, and the timing belt (which he may have reffered to as a drive belt if he was old, lol)
Edit Edit: PM RubyRS4 on here, he would be able to do most, if not all, of that stuff.