Cross sections for state changing collisions of Rydberg atoms with polar molecules have been calculated using a classical trajectory Monte-Carlo technique. Although the dynamical problem was restricted to two dimensions, useful insights into the full three dimensional system were obtained. For example it was found that at thermal velocities the Rydberg electron can collide with the molecule many times during a angle trajectory. This implies that the impulse approximation, which is commonly used for many Rydberg collision problems, is not valid for this problem, since it cannot account for this effect. Finally, a finite effective range for the dipole interaction was observed, which can be used to make the calculation of three dimensional cross sections more tractable. Without these insights, the three dimensional calculation would have been much more difficult and costly.