1.
Download the Steam Deck Recovery Image from here
2.
Download Rufus Standalone from here
3. Open Rufus and make sure the correct target drive is selected, sometimes you need to check the 'Show USB Drive' box. You can use USD Thumbdrive or SD card
4. Press 'Select' and choose the Recovery .img file
5. Press 'Start' and complete process
6. [OPTIONAL but Recommended] Drain your Deck of power below 50%
7. Shutdown. Then reboot pressing 'Volume +/up' + 'Power'.
8. Select to 'Setup Utility' -> 'Power' -> 'Battery Storage Mode' -> 'Yes'. The Deck will shut down
9. REMOVE THE SD CARD IF IT'S INSERTED!!!
--->The next part is easiest done by placing the Deck face down in the top part of the case like it would be with the case closed
10. Using your tiny screwdriver remove the screws on the back. [OPTIONAL but Recommended] Layout the screws out in the same manner they were removed so you put them back in the same place.
11. Use the guitar pick/opening pick on the right side at about the button height to pry open the shell. On the old models it was easier by the exhaust vent
12. Carefully open and remove the shell
13. Remove the metal shield screws at the top and bottom then remove the metal shield
14. Carefully use your plastic pick to unplug the battery. The old models have a pull strap(Don't use this), the new model doesn't
15. Remove SSD screw and remove the SSD
16. Carefully slide the shielding off the drive. You don't need to damage it like iFixit says
17. Slide shielding onto the new SSD and install it along with the SSD screw
18.
Carefully plug your battery back in. Easiest to use the little protruding plastic parts on each side
19. Put metal shield back along with screws
20. Snap your backplate on, but don't put your screws in until you've verified functionality
--->
21. Plug your charging cable in and power your Deck up to wake it out of battery storage mode
22. Shut it down
23. Insert SD card or plug in USB thumbdrive using USB-C hub
24. Use 'Vol -/down' + 'Power' to enter boot menu then select your SD card or USB drive
25. It will boot into KDE Plasma desktop. Select 'Reimage Deck' and Yes/Proceed. Then reboot and the Deck will boot into SteamOS
26. Shut it down then replace the screws
27. Power up the Deck and it will be ready for login and play