We have two 5545-X ASAs in active/standby mode that currently run sfr module 18.104.22.168.
Our plan is to upgrade our FMC from 22.214.171.124 to 126.96.36.199 through proper upgrade process. However, for our ASAs, we are planning to re-image them straight to 6.2.0 and patch 188.8.131.52.
My main question here is, can I install firepower module on standby first and then install on active firewall without having to do a failover ?
Yes, you can. the modules installation is independent of ASA failover. You can install the module on both 1 by 1 and then configured the service policy later without having do failover or affecting traffic before the redirection is configured.
Hope it helps.
Note that service-module health is a failover criterion by default. It can be disabled since ASA 9.3(1) and higher.
If you don't disable the monitoring, shutdown or reload of a Firepower module on the active unit will cause a failover event (or status of "not ready" in case it is reloaded on a standby unit).