Safe first flash on a P12 I6 2006 Envoy

I just want to make sure I dont mess anything up. I see where some other people have had issues here on the site when flashing these PCM's

Im probably going to have the Dealer update the PCM with the Latest firmware to fix the idles issues this car is having (As they have rectified the aging Cam modulator with PCM updates) then do a read and make some further modifications to the computer.

Any suggestions to being successful?
-other than updating EFI live to the latest version before starting.

Thanks

I should be able to just pull down the calibration and modify it then upload it again correct?

Looks like those posts from a failed flash were back in 2010 so Im guessing its all rectified now?

Thanks

Pulled the stock tune down and the tables are totally different than the LS1 computer setups.