unextracting parts? MS 3

I have a 17 part piece. Made changes to some parts and mistakenly believed I had to re-extract them. The result is I have several sets of parts. Now when I make changes to individual parts in the first set, then Export to pdf, and Replace all Parts, the changes don't appear. The pdf seems to be of one of the other sets of extracted parts. Question in general, is it possible to delete a Part once extracted in MS 3 ? thanks. Loving MS.