By that time it had become slightly damaged, but it is still in good enough shape that you can see that the same kind of plant still grows today in Montana. Definitely longer than 20 or 40 thousand years. Under ideal conditions in a laboratory, it takes 25 hours. It takes less than 32 years, if the conditions are right, in nature. Answers in Genesis has an excellent web page about Instant Petrified Wood .
Fossilization depends upon the proper conditions more than on length of time.
If the required minerals are in solution, then they will replace organic material in very short order. If the required minerals aren t in solution, then thousands of years can go by without fossilization. None of the invertebrate shells that I found in Montana around the hadrosaur eggs were petrified. The invertebrate paleontologist on the dig was not the slightest bit surprised that the shells weren t fossilized. Also, maybe you should date moon rocks, since you believe that a lack of dust is proof of a young universe.