Running ubuntu 14.04 with a Gnome3 Desktop i have second thoughts on removing Oolite v 1.77.1. In the Directory /home/GNUstep/ there are only 2 files: /Defaults/oolite.plist and library/Caches Oolite-cache.plist. I'm not exactly familiar with GNUstep, but i wonder if savegames still work when removing or purging the package scince oolite.plist seems to contain various information about savegames as also equipment or Game options.
Removal of the package - even with the purge option - shouldn't touch files in your home directory.
is where some of the game settings are stored. So long as you don't mind resetting a few things it's not a big deal if you lose it, but you may as well keep it around to save time after the upgrade.
contains processed OXP information for quicker startup time. It'll be discarded as too old anyway when you install a new Oolite version.
Save games don't depend on either file - you can copy them around as you like. Again, removing the package shouldn't affect them.