Here are the steps to replace the CRU in a Cache Group environment

CF_A: Cache Group Manager (to be replaced)
CF_B: Cache Group Member
CF_C: New CRU

1) Elect CF_B as the new Cache Group Manager and remove CF_A from the cache group

CF_B#(config)cache-group become-manager

CF_B#(config)sh cache-group <-- ensure that CF_B is now the new Cache Group Manager

CF_B#(config)cache-group manager

CF_B#(config manager)remove member <CF_A serial number>

2) Re-direct production traffic away from CF_A and power down the unit

3) Move the components from CF_A to CF_C as per the instructions at:
https://bto.bluecoat.com/sites/default/files/tech_pubs/CRU_Installation_Guide_SG_CF_AV.pdf

4) Power up CF_C once completed

5) Downgrade or Upgrade CF_C to the same version as CF_B

6) Now you are ready to join CF_C to the cache-group

7) On CF_B, check if the Authorization Mode is "open" or "strict"

CF_B#(config)cache-group manager
CF_B#(config manager)view
CacheGroup Settings:
Management Port:      8087
Management Interface: 0:0
Authorization Mode:   strict <--

8) If it's "open", you can have CF_C join immediately. If it's "strict", add CF_C's serial number to the cache-group by executing:

CF_B#(config manager)add member <CF_C serial number>

9) Finally, join CF_C to the cache group as per below. A restart will be required on the cache-group member to sync the config and setting

CF_C#(config)cache-group join x.x.x.x
A reboot will be required. Proceed? Y/N [N] y
Manager reports serial number: <CF_B serail number>
Is that the expected serial number? Y/N [Y] y
  ok

10) Once online, CF_B will be the cache-group manager and CF_C will be the member. If you want to make CF_C the manager, apply the command:

CF_C#(config)cache-group become-manager