I already cloned my launch Deck onto a external hard drive with Clonezilla a few days ago. Realized i didn’t have the correct size torx screwdriver, so i had to wait a few days to get one. I’m going to open up the OLED to put in a 2 tb SSD, and then use Clonezilla to install my Deck image. Should be no problems, right? Firmware was updated a few days ago, so it’s up to date. I think it was 3.5.5 or something.
As long as you updated to 3.5.5 Stable before, you should be good to go.
Just clone your drive and you are good to go.
Unless you messed with the partition table to add a Windows partition, SteamOS will automatically expand your home partition to the full size of the disk on bootup.