those caryard warranty's only cover certain parts of the car, say your diff is stuffed, it will only cover certain splines etc in the diff, and if its caused by other parts that broke off first etc, then damaged them it wont be covered. its all a scam, think about it, why would a car yard wanna pay out thousands of dollars for things that can break from wear and tear, i dont think so.
Anyway i bought my car second hand, i searched for months for the right one, i finnally found one i had throughly checked over by racq, inspection at the time, bcoz it was in brisbane not aroudn where i live, other wise get some friends, and go look at the car, look at all things like underbody for dings and scrpaes and chassis rail damage look for rust, around boot engine bay, windscreens etc, dont be shy to pull out the boot lining and have a look around, then if u are happy with the initial inspection, tell them u will be in contact for further inspection, then book in a time for the car to be inspected at racq service centre or a trust worthy person u know or trust. then if compression test comes up good and all other things look good, and u hae ticked all your boxes, then u mite have a good car on your hands. but its really common sense, basic stuff u would look for on oyur own car for inspection, look for on that car, oil leaks etc, damage. good luck with it.
Daz