When I import a picture on a black background that I want to change to white,the program will do a global remove of most of the black but leaves alot of black right up against my picture. Then when I click on a substantial section of black near the picture and hit delete, it doesn't do anything. It's extremely time consuming to remove one block at a time. Is there a way to really remove all the dark background at once?
You can do global removed of entire colors -- like all black but that does remove that color within the body of the image. You can mark off sections of the pattern and do a global remove within the selected area. That is more time consuming but at least preserves most of the foreground.
What sounds like is happening is you are getting a lot of "near black" that is not quite black that is not affected by your global removal. You would have to do the same thing with those colors.
What might be easier would be to edit your picture and try to flip the background to white instead of black.