The beginning of the end is here, the year end that is. Microsoft Dynamics GP Year-End Release 2015: Install & Upgrade
Microsoft Dynamics GP Year-End Release 2015: Install & Upgrade – Microsoft Dynamics GP Community
Install, Upgrade & AdminYear-End & 1099
Archived post from 2015. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.