I have a mild grinding/screeching noise coming from my steering wheel when I turn significantly

The sound will probably be originating at the points I mentioned. When the steering wheel is turned as far as it will go, there will be more resistance on the pump because it thinks it should go further. That puts more load on the drive belt and it doesn't like it so it slips on a drive pulley and complains by making a whining noise.
The steering column between the power steering end and the steering wheel in your hands is like an exaggerated stethescope and the sound gets transmitted through to where you are hearing it.
If you turn the wheel until you start to hear the sound, and then relax on the turning pressure and the sound stops, you should have isolated the problem. The sound will probably be originating at the points I mentioned. When the steering wheel is turned as far as it will go, there will be more resistance on the pump because it thinks it should go further. That puts more load on the drive belt and it doesn't like it so it slips on a drive pulley and complains by making a whining noise. The steering column between the power steering end and the steering wheel in your hands is like an exaggerated stethescope and the sound gets transmitted through to where you are hearing it. If you turn the wheel until you start to hear the sound, and then relax on the turning pressure and the sound stops, you should have isolated the problem.