You're welcome! Best of luck with it.

I had to take my Acer CB5-571 apart to upgrade the drive. But obviously it may depend on the exact model whether something might be soldered in. Mine came with a M.2 16GB drive and no touch screen, so obviously a different model. Here is a video similar to what I did to upgrade the M.2 flash drive. I went with the 128GB size because it seemed like the 256GB size was if-ier for compatibility.
https://www.youtube.com/watch?v=B3Ud-ReH50o

One reason I upgraded the drive in size because the original drive in the Chromebook failed at some point. In addition to a 128 GB M.2 drive, I also bought another 16GB M.2 drive because I was not sure about compatibility (which turned out to be useful as mentioned later).

You may never need extra space depending on what you want the laptop for though. And more easily, you can also just use, say, a Samsung 128GB USB 3.0 Flash Drive Fit (MUF-128BB/AM) in one of the USB ports if you want lots of storage (maybe with a slight battery life loss or perhaps slower drive performance). I find such a drive also warms up a lot when I do a lot of copying to one for backup though.

What I went through with the changeover was a little complex since the first time I installed GalliumOS I did not upgrade the firmware first or, alternatively, us the MrChromebox scripts to set the GBB flags. Instead just set the dev_boot_legacy flag from the ChromeOS command line (which requires battery power to maintain and tells the original firmware to do a legacy boot). Then I accidentally let the battery run down when using the original firmware (when away on a trip) and lost that special boot setting (a peril mentioned on the "Installing" and "Firmware" pages). I could not figure out how to change that boot setting again without temporarily swapping in another M.2 drive and installing regular Chrome on that one -- since I had wiped Chrome entirely and not done a dual boot, and I did not want to overwrite the existing GalliumOS install with ChromOS via a USB-driven install and lose my user data. And I don't think you can boot from USB without that flag being set (as implied on the "Firmware" page).

I also installed GalliumOS the first time without UEFI booting or the firmware upgrade that makes that possible. I wanted to upgrade the firmware to avoid that battery-run-down issue affecting booting in the future and to also get rid of the possibility of someone wiping the drive by pressing space on startup. But then I also switched to UEFI booting after upgrading the firmware (I didn't have to switch, just wanted to try it). That meant my old GalliumOS install would not boot becauge I had installed it under the legacy boot setup. I could not easily figure out how to upgrade the existing install and repartition correctly to have the needed UEFI boot files in the right places. I ended up deciding to just wipe the drive and start over with a fresh install (and then restore a backup of my user data I made before starting the firmware upgrade). I think an in-place upgrade from legacy to UEFI boot should be doable -- especially if I had had a working UEFI install on another Chromebook to examine and copy stuff from. But people online just said wiping and reinstalling was a lot easier given the need for a new partition scheme.

But I learned a bunch along the way, so that was good. And if I had just upgraded the firmware in the first place and gone with a UEFI install from the start, I would not have had those other difficulties.