I've been using Ubuntu for about 20 years, but I'm perpetually noobish so please spoon-feed me information if possible!

I managed to build eduke32 from source, and I downloaded a shareware copy of duke3d using game-data-packager. At the initial startup of eduke32 I selected my shareware version of the game and I think I ticked a box to "always use this version" or "never ask me this again" or something like that. Now some time has passed, I've completed the shareware version and I want to upgrade to the full game.

How do I get eduke32 to show me that initial GUI again, so I can point it towards a different set of game files? Or, is there a way for me to upgrade/replace my existing game files to upgrade from shareware to the full game?

Thanks in advance, I absolutely love Duke Nukem and this game has shaped my life from a young age!

UPDATE: I may have just figured it out. Here's what I did:
1. I used a virtual windows machine to unpack the setup.exe file of the full version of the game
2. I transferred the game files over to my Ubuntu machine
3. I found the duke3d.grp file belonging to the shareware version in the folder /usr/share/games/eduke32/
4. I replaced that file with the duke3d.grp file belonging to the full version, which I had transferred over from windows

So far it seems to be working. But I'm confused about what all the other game files were that I transferred over from windows. Are none of them necessary for running the game? I'm wondering if I might run into problems down the line, like when I encounter sprites, enemies, or weapons in-game that weren't part of the shareware version. Should I move any other files into the eduke32 folders?