If you are a 9.5 release or lower, just shut the machine down, swap the processor card and install the flash card (make sure you do a "save trans" before shutdown) and power up.
Now if you are a 10.0 or later release you better get Avaya involved and be prepared to spend a few bucks, because you will have to have the license file reinstalled with the new processor serial number, otherwise the switch will shut down call processing after a short time, due to a license file error. Good ole' Avaya.