Took us almost 4 years to change from non-radar-procedures to radar vectoring in my previous APP/TWR.
Not only we had to train : most of us had been trained and qualified on radar before coming to this TWR.
Procedures with surrounding APPs, ACCs had to be created and tested first.
At the beginning, the radar system came in. We had no right to use it for vectoring : only surveillance.
Then procedures and training for radar vectoring on arrival only.
Finally, procedures and training for vectoring on departure.
I was about to forget : a new tower had to be build because the ancient wasn't fit for purpose. And the furniture had to be moved twice in the new one because the architect had placed us back to the runways.
I guess things can be done much faster, but beware of doing things too fast for political/economical reasons : this kind of (too) fast decisions can lead the wingtip of a 380"super" straight in a building... don't want to figure what could happen airwise.
When is that London Olympic thing, again ?