I bought the part and tools from iFixit and followed the directions. The mechanical part went smoothly - maybe 10 minutes to disassemble/replace/reassemble.
Getting Catalina (the current MacOS) to install was not working until I used Cmd-Opt-R (as noted in the OWC paper sheet that came in the box) which brought up the proper installer - I believe from a pre-prepared bootable SD card but it’s hard to say. From there the install succeeded taking ~1.5 hours.
Beware that (a) the install requires a working internet connection for verification and updates, and (b) the system must have been running at least macOs 10.13 (High Sierra) before the install in order to have an EFI BIOS that recognizes the SSD.