If there are no voids, then no, you don't need to. Stabilizing will make it easier, but you need Cactus Juice, a vacuum pump and a vacuum chamber (or Bell jar), and an oven.
You can find somebody here to send them to for a fee to be stabilized.
You can turn them as is, just cut lightly with a very sharp tool. Cut about 1/32" proud of final thickness and sand to finish it.