Hey guys, I'm taking the plunge and I'm going to buy the DN3D expansions (Caribbean and Nuclear Winter). I got Duke it out in DC in the mail today, and I'm just wondering how I'd install it to play it from GOG's Duke 3D Atomic. Any help would be greatly appreciated!

I'd like to know this myself, and why Duke It Out In DC and Nuclear Winter AREN'T on GoG

Carribean and Duke It Out In DC while not part of canon are good in terms of quality what can't be said in Nuclear Winter case, as this is weakest from all these three but also fun. It shoudn't be hard to implement them in way like Shadow Warrior Complete is already (simple dosbox script). Also Duke Extreme has few interesting enemies and weapons.

They aren't here probably due to licensing problems.