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Hi,
How did you install AutoCAD 2013 in Yosemite? Which installer did you use?
If you used the current installer avaliable now in downloads section of Autodesk Support site:
http://knowledge.autodesk.com/support/autocad-for-mac/downloads/caas/downloads/content/autocad-2013-...
than it already contains all SP integrated and you don't need to install SP manually.
As about "hang" when you are trying to run uninstaller, than - have you tried to reboot your Mac and run uninstaller again?
Maxim