Big-IP LTM Device Firmware upgrade

My Big-IP 20000 device currently run on 12.0.0 HF3 firmware but recently my iHealth has been advising that i upgrade to latest firmware version which is 13.0.0 HF2. My questions:-

1) I need step by step procedure on how to carry this upgrade out 2) The likely effect it may have my network 3) I will like to know whether it is service affecting 4) What happen to the present configurations on my F5 devices, i.e. will the configuration be intact after upgrade? 5) My devices are setup on Active / Standby topology, do i need to do the upgrade on the two devices separately or it can be synced across after the firmware is upgraded. 6) What other things do i need to know before embarking on the firmware upgrade.

Thanks

Taiwo