Is it bad to go over 3000 rpm?
Running an engine some 3000 RPM below its redline should be absolutely find for extended periods of time. So long as your oil and coolant is in good condition, timing belt in good order etc, then most engines will handle this sort of driving for hours per day.
How many RPMs is too high?
How many RPMs is too high? Typically, engines idle at about 600-800 rpm. Older engines may go up to 1200 rpm or more while warming up. But if the engine is revving up while idling, even after it's sufficiently warmed up, you might have a problem.