I imagine it would be very difficult, but possibly worth trying. Gorillas are pretty specific about only eating what they have learned is safe, and like chimps and other animals, they self-medicate with leaves and herbs they know will help with various ailments (like bellyache or worms). The young ones learn a lot from the adults, so just transplanting young ones wouldn't be likely to succeed. But that's about all I know - any Great Ape experts amongst the 'catters?

Then again, you could check out what the Canadian beaver has done to those Argentinian islands...