Surely that was a typo - it's not really idling at 2500 RPM is it? Normal idle is around 700 RPM (I'm not sure of the exact specs for your engine). If you had to set the idle that high just to keep it running, something's very wrong and the shaking is probably due to it misfiring badly on a couple of cylinders. I definitely wouldn't drive it until that is fixed, and wouldn't even let it idle any more than necessary. And no, it shouldn't try to shift gears when in park, no matter how high the RPM.
Tell us more details about the problem and maybe we can walk you through a diagnosis. When did it start doing this? Who set the idle so high and why? Does it always run rough or just sometimes? The more info you give, the better.