I just finished installing the new drive and flashed the OS. Just booting into Steam OS literally as I begin typing this. I'm not sure if it really is the same OEM drive as my 512 GB Deck because they report slightly different sizes.
The newly upgraded Deck reports a maximum of 463.4 GB from the Storage menu, whereas my original 512 GB Deck reports a maximum of 465.3 GB. Even so, that's close enough for me! Now I can scavenge the 256GB microSD card I had put into what was the 64 GB Deck and use it for even more storage on mine. 🤓 Though, with it being slower, I'll have to remember to put only smaller things on it, such as ROMS or small indie games, or personal documents/project files from Desktop Mode.
I have no problem opening up a desktop PC or even a laptop, but I was pretty intimidated about opening up the Deck. I did have a little bit of trouble because I don't have a "professional" screwdriver/repair kit with all the accompanying tools. The first screwdriver I tried was too pointy for the shallow notches of the screws and didn't always catch, so I couldn't spin it. The next screwdriver I tried worked better but the bit was too large to fit into the deeper holes. Then I got out my "precision/jeweler" screwdriver set, but they're tiny little things I can never get a good enough grip on to apply torque with any real force. So I had to use some pliers to grip the precision screwdriver while forcing it down into the screw-hole and finally loosened everything up enough to get all the requisite screws out.
Then the next hard part was separating the back of the plastic shell from the front. I don't have a spudger so I grabbed a LEGO separator tool which did the trick, but I noticed after the fact that it did ever-so-slightly damage the plastic of the Deck at the location where I first stuck it in. But it's so slight that I doubt anyone else who uses the Deck would ever notice. Then, to separate the shell on the outside of the triggers, I had to push the LEGO tool down the crevice near the trigger and the seam between the front and back of the shell and twist/pry it slightly to get it to separate enough to insert a flathead screwdriver (because I didn't have anything else to use as a spudger) to gently pry it apart the rest of the way. Once I got it started like that I was able to use the LEGO tool to finish going around the sides and bottom of the device up to the other trigger, which required the same trick as before, though with less force. The whole thing would definitely be easier if you have a nice electronic device repair kit with decent screwdrivers and a couple of spudgers.
Once I got it open it was pretty smooth sailing, with the only other hiccup being that the 64 GB drive had a little metallic sleeve around it for some kind of shielding. The 512 GB drive is slightly thicker than the 64GB drive so I couldn't get the shield on without loosening it a little bit. That just involved pulling back the adhesive, putting the drive in the shield, and then re-adhering the shield back together. Then I put everything back together and flashed the OS and it's good to go. All in less than an hour even with my minor setbacks. In fact, it took me almost as long to write this post as it did to actually change out the drive and boot the Deck back into Steam OS. 😅
In short, even though I was intimidated at the prospect of opening it up, I feel it wasn't that big of a deal now that I've done it and I would have no problem opening it up again if necessary.
Now, what to do with the spare 64 GB EMMC module I have? I wish I had a more modern computer with a few empty M.2 slots I could put it in. . .
