Doesn't need to be super expert, but should definitely know their way around Windows Server (2016 or greater)
Term unknown, 6 months +, maybe a year, maybe more
Guide others with knowledge of A/D replication, DNS, user authorization, Group Policy, etc.
Must write documentation following templates provided by the County
Must be very proficient in understanding and writing documentation for the team
Willing to pay more for greater expertise, but the term would be diminished; that is, I'd pay more for a true expert, but the term would almost certainly be limited to 6 months to meet the budget