Specific Changes Validators Need to Make for the Chang Hard Fork?

Node Upgrade At least 70% of validators are required to upgrade their nodes to version 9.1.0 or later to make sure that there is compatibility with the new governance features​.

Participation in Governance Validators will also have a key role in voting on governance proposals using their delegated ADA. 

Support for New Protocols Validators must make sure that their infrastructure is ready for changes in transaction processing and the smart contract functionalities introduced by Plutus V3 enhancements​.