For your parts question: go into the plot options and make sure an option along the lines of "only for shown parts" is on. Then hide the bodies in your analysis tree you want to not see. Lastly, refresh your plot, by hiding and showing again.
As for your second question, I am interested in that too.
For "removing" stresses. I have had good luck using Isosurface plots. You can at least limit, or isolate the stress values you do not want to see, with two or more iso-surfaces by directly typing-in the values that you want to have plotted, and the values in-between do not show up. Hope that helps. -Tony