Is percocet the same thing as oxycodone?

No. Although the opioid component is the same (oxycodone), Percocet includes Acetaminophen (tylenol) which in fact sets the limits of the maximal dose allowed.
Not quite. One of the active ingredients in Percocet is oxycodone, but Percocet is the specific brand-name of a medication that combines oxycodone with Acetaminophen (the active ingredient in tylenol).