Reloading 3.0.1 over 3.1

I now have ArduCopter 3.0.1 loaded on my APM. To keep current I would like to update to 3.1, but if I end up having the blown 3.3v regulator issue, how can I reload v3.0.1? Thanks

It would be good to check the 3.3V line’s voltage before upgrading. The instructions on how to do this are on this diydrones discussion which you’ve probably already seen but I’ve updated it recently.
If the voltage is fine then we’re pretty confident that you won’t see the dreaded “Bad Gyro Health” message after upgrading to AC3.1.

 To reload AC3.0.1 you can go to the Mission Planner's Install Firmware page and on the bottom right you'll see a link to "Pick previous firmware".  Select the top item on the list and you'll see the versions underneath the icons all change back to AC3.0.1.

Good advice, I will check the 3.3v first and upgrade to 3.1 if the regulator voltage reads OK.
Thanks for the quick response.

Measured 3.3v on the button, loaded 3.1, happy flyer.