No big deal for the D, they intend to use both formations from Pettine/Ryan and Schwartz.
The O will take longer, new scheme, new coaches and a lot of new players.
Good question, I'm guessing now.
Practice? You can't teach a guy speed, you can't teach a guy to be 6'4", but can you teach a guy to read defenses and accuracy? Maybe, depends on the guy and who coaches him.
Why the hell haven't the Bills signed any London warehouse workers? What is wrong with Whaley? The Bills front office is always behind the curve. This team is never going to be competitive until they get a franchise London warehouse worker!
I saw Gilchrist play. If Gilchrist had taken the usual route to the AFL or NFL he would be considered one of the greatest of all time. He didn't start playing professionally in the US until he was 28 years old.