Anyone who has successfully modernized their data governance, how long did it take to adopt a new approach?

This is an intriguing question that, given the current landscape, is entirely valid. 
We are currently in the midst of modernizing our data governance framework, a process we are undertaking in collaboration with key technological partners. 
I would suggest to proceed by engaging these key people and not only external partners or consultans for a one shot activity as well as to ensure the support from top management: effective data governance requires commitment and understanding from the highest levels of the organization.

Anyway, building a culture of data responsibility and understanding across the organization is key.