Viprion 2400 -- migrating from 2150B to 2250B

  can you please let me know what issues have you seen when you replaced the blades. Did you follow the process that   mentioned above. Also had few questions

1. is the base registration key tied to the chassis/blade and do we need to do a license transfer from 2150 to 2250.
2. i saw that on f5 documentation they mention about using modify sys crypto master-key prompt-for-password for encrypted password. Also saw f5mku -K for ssl profiles. Should we use both or is using the master-key is good for ssl profiles and user passwords?

if anybody has used this please let me know your experience with it. I am a newbie, Thank you for your help