Originally Posted by
Money D
from what I've read, internal means taking everything apart and using new cables/etc.
New Di2 cables are not needed unless the new bars are radically different from what's on the bike now. If the Di2 cables on the bike now have a little slack then you can reuse what's already there.
It might make sense to replace hydraulic hoses. At a minimum, I'd check for spots where the hose might be wearing through but if not worn then replacing the hoses is not necessary.
-Tim-