I've noticed when I am trying to move part of a model by using the arrow keys, instead of being able to nudge that part in whatever direction I want it to go, I end up cycling through different parts of the model? I'm not sure why this happens, I hit the "N" key first to go into Translate mode, and then try hitting the down arrow to move the part down, but instead of the part moving, I end up cycling to another part of the model. It is starting to drive me loopy, since I'm not sure what I am doing wrong.

If you select a Group or other element in the PWS then use the cursor keys you will change your selection to whatever is listed above or below in the PWS.

Re-click on the selected thing in the model window after you select it from the PWS, then the cursor keys will nudge in the model window.

I have been caught by that dual functionality occasionally.

The other one that I a reminded of is the fact that the 7 8 9 0 keys can either set a view mode or set a channel interpolation mode depending on what window you are in.

yep, a lot of keys are "window-dependent" for want of a better term. I've set keyframe interpolations when all I wanted was to switch views and it confused the heck out of me the first few (dozen) times!