Hi Ed when you took the old screen it should have been connected to the handset by an thin ribbon like cable and a small socket if not it may be connected by contacts on the back of the screen i would suggest you remove the screen from the other handset carefully and make note of how it connects and just reverse the process to fit it into the other phone, tip a guitar pick is excellent for removing phone covers as it doesnt damaged the cover, nokias are quite easy to replace parts on, I have changed a few screens you just need to take your time and be carefull also you could try googling the subject as there are lots of forums with detailed repair guides.
Mike Smith, September 2008