Totally agree on the diagnostic charges, I used to get ripped off but then I found a very nice guy who does it for free sometimes.
brakes pad can't be that exp I just got mine changed and it cost me 7k for all four
transmission bottle from zic costs 458 per liter so I think max 4 litres will go into it (not sure)
also the main thing will be your belts that's probably the most exp thing in the list.
I don't think you will face any difficulty in sourcing parts, it's a Prado they are very common these days.