Maya 2013 Service Pack 1 is a full product installation. You will need to unisntall your exisiting Maya application before installing this release.
This service pack includes all of the fixes from the hotfix releases that preceded it. Therefore, you do not need to download and install all of the hotfixes in addition to this service pack.
You can download it here:
For more info on what is fixed, go here:
Thanks to Nelson Cruz on the Maya Station.