Welcome Pat!
Jump onto the US forum here:
1999 - 2003 7.3L Power Stroke Diesel - Ford Truck Enthusiasts Forums
Note: The Aussie 2005 = the US 2003 7.3. Towards the end of 2003 the USA dropped the 7.3 and went to the 6 liter. The 7.3 production was moved to Brazil and continued there. Ford Australia imported the Brazilian trucks and released them here as RHD until 2006. There are also a fair few personal imports of US trucks too, with RHD conversions of various qualities depending on the firm doing the converting.
There is a huge body of knowledge and following of the 1999-2003 7.3 in the US. Read through the US forum, search & learn. The documented 'weakest link' is the 4R100 auto transmission which itself can be replaced with bullet-proof US customs made jobs.
Many of the trucks are getting miles on them now, members of this forum have in some instances inherited problems from the PO (Previous Owner).
Read up on the transmission, HPOP (high pressure oil pump), plus the usual stuff with any used vehicle, verify service details, get someone to scan the computer and check what the codes are - some can be safely ignored, others can't.
Post questions as you go.
Probably the best advice I've learnt is buy the best example that you can find - a problem avoided is a problem solved.
Also for me, by far the F250 has been the most rewarding vehicle that I've owned. I've met a great bunch of guys and learnt a lot of stuff, not just about F250's. If you can afford to have the truck off the road if issues do arise, there is nothing that can't be fixed at a reasonable cost, most of the time by avoiding 'stealerships' (Ford Dealerships) - although I did buy a transmission gasket & filter at one.
Every other service item on my truck has been sourced directly from US suppliers (e.g. RiffRaff Diesel) or from NON-genuine parts - e.g. Baldwin filters.
The most recent horror story was someone was quoted $6000 from a Ford dealership for an F250 alternator. You can buy a heavy duty alternator from the states for $275 + freight (how quick do you need it?).
Consequently, a lot of Aussie F250 owners who do NOT take an interest in their vehicles can get screwed pretty badly, and this seems to happen to US owners in the states as well.
If you're prepared to learn about the vehicle and chase solutions, go ahead and start looking.
On the otherhand, if knowing about what you've driving is way down on your priority list, IMO you would most likely suffer less stress & aggravation by walking away now.