you do not need to destroy the old one. just upgrade via servicepack. after applying the update and the system shows the license issue, just restart. now the license is valid for 3 days. in this time you can request a new one at support@proxmox.com.
cluster: please run proxca -k after you upgraded both nodes (to exchange the new SSH keys)
during the next few hours release notes and howtos for the service pack are published.