My grand prix shakes when i go up a hill or start out. i have good tires

If the shaking is caused by the engine missing (a misfire on 1 or more cylinders), then
check your (a) spark plug wires - pull each and check for continuity/faults/burn marks/etc., (b) spark plugs - pull each & check for fouling/faulty/etc.
Another good check for spark plug wires is to park in a dark area at night (open garage with the
lights out works), run the engine and observe the engine operate in the dark - little lights caused by
faint arcing means that the wires are leaking electricity to the engine block, instead of delivering it
to the spark plugs, like they should.
Your particular car has a Distributorless Ignition System (DIS), consisting of an ICM (Ignition Control
Module) connected to an individual coil pack for each pair of cylinders. You'll need a
HEI (High Energy Ignition) ignition system tester (about $30-$45 any auto parts store) to test
these coil packs, which I have found quite easy to replace (usually a couple of 10mm cap screws).
Since the car shakes only when accelerating or going uphill, I tend not to think that suspension
components of the car are at fault.