I just transplanted a nearly 6-foot Australian Pine that was in a pot. I followed instructions from another web site I saw, but my question is how long after transplanting it will I know if it is ok or dying?
Newly planted trees are vulnerable for up to a year after they are planted. If it does fine for a year, then you can consider it established. For the next year, look for yellowing or dropping needles to indicate if the tree might be failing.
This is an Australian pine at least 5-6 yrs old and is over 20 ft tall and trunk is approx 5 inches in diameter. It grew straight but is now leaning.
Austrian Pine trees are quite disease resistant but they can become infected with a root feeding nematode.
Phytophthora and Hetrobasidion root rots.
Have you had excessive rain to loosen the ground and root system?
With the size of tree your dealing with I would certainly have a professional arborist look at the tree to determine the best coarse of action.
Here are a couple of links for you.
https://www.gardeningknowhow.com/ornamental/trees/tgen/straighten-tree.htm
https://extension.psu.edu/pests/plant-diseases/all-fact-sheets/pine-diseases
Needles have all turned brown and this is what I found when cutting it down
I believe these are the eggs of the European Red Mite. I would remove the eggs and dispose of them.
Treat the tree with an insecticide that covers this pest; check with a local garden center for product in your area.