Secure 3 Servers – SSH Hardening, Port Change, Fail2Ban & Security Enhancements

I need an experienced Linux server administrator to help secure my 3 servers. The tasks include:
Disabling password authentication for SSH (use key-based authentication only)
Changing the default SSH port
Installing and configuring Fail2Ban for intrusion prevention
General server hardening (basic security best practices)
Review current setup and recommend/implement any additional security measures (e.g., firewall rules, root login restrictions, updates & patches, intrusion detection, log monitoring, etc.)
Requirements:
Strong knowledge of Linux server security (Ubuntu/Debian/CentOS)
Experience with SSH configuration and hardening
Familiarity with Fail2Ban setup and security best practices
Must ensure servers remain fully accessible after changes
Deliverables:
All 3 servers secured as per the above requirements
Any additional recommended security configurations implemented (after approval)
Documentation of all changes made for future reference
Notes:
Access will be provided via SSH
Need this done within 1–2 days