The Surface Laptop 3 is the first Surface device that Microsoft has made with replaceable storage, and now there are official instructions for how to swap the SSD. Microsoft watcher WalkingCat on Twitter was the first to find them. The instructions can be downloaded here (opens in new tab).
Microsoft's manual, entitled "rSSD Removal Guide for Enterprise" shows how to make the switch for both the 13-inch Surface Laptop 3 both with and without Alcantara, as well as the 15-inch Surface Laptop 3. In this case "rSSD" is short for removable solid state drive. In this case, it's a shorter, M.2 2230 drive.
Besides going through a series of warnings and a list of tools (which it suggests getting from Amazon, iFixit or other retailers), it's interesting to note that there are differences between the metal and Alcantara versions of the Surface Laptop 3. The versions with the fabric require suction cups to open, per the instructions, which the metal ones don't.
There is still some adhesive under the feet, and Microsoft suggests technicians replace those entirely to provide new adhesive to ensure a proper fit when returning the device to a customer.
The tools necessary include a Torx-plus 5 screwdriver, a spudger, suction cups, replacement screws and feet and a suggested anti-static wrist strap.
iFixit previously tore down the device and gave it a 5 out of 10 points for repairability, suggesting the Surface Laptop 3 marks a huge improvements over previous versions, which were entirely glued down.
Microsoft doesn't consider the Surface Laptop 3 to be user upgradeable, so if you attempt to perform the upgrade yourself, you'll likely void your warranty. If you don't know what you're doing, consider going to a professional.