Is 2, 000mg of acetaminophen in one dose too much?

Don't do it again. This won't hurt or kill you, but you do need to show this helpful drug the respect it deserves. It's important to space the doses out so that you don't get sick. Up to 4000 mg/day is fine but you don't want to take even this much all at once -- you might overload the enzyme that processes it by the normal pathway.
Yes. Too much. Maximum recommended at one dose is 1000 mg with max of 4000 mg total per day. This daily max is expected to be lowered soon. Higher dosage can harm your liver. If you have taken that much, degree of damage may depend on how long you have been doing that. Your doctor can test your liver enzymes to get an idea of how serious your condition is.