Earlier this month, Surface boss Panos Panay showed you how to get into the Surface laptop 3 by lifting the top plate to iFixits Outline of Surface Laptop 3.
Previous Surface Laptops were not easy to open at all. They had to forcibly pry up the keyboard and top cover to access the fixtures – iFixit used a knife for the surface laptop – and when they finally came to these fixtures, it turned out that none of them could be replaced by the user. It was so hard to work with iFixit that both the Surface Laptop and the Surface Laptop 2 were rated 0 out of 10 with four Torx Plus screws on the bottom of the laptop. Then you can gently lift the top cover, which is attached to the rest of the computer with magnets and a single flexible cable, with a plectrum or other soft prying tool (perhaps even a fingernail?).
However, once you have removed the cover, you can no longer configure the Surface Laptop 3 to your heart's content because the CPU and memory are soldered to the motherboard. The only thing you can easily replace is the M.2 2230 SSD, if you can actually find one.
Microsoft warns against sharing them, saying that this should only be done by an "experienced technician," but the only thing keeping the SSD down is a single Torx Plus screw. So, if you know exactly what you are doing and are willing to void the warranty, you can apparently add storage to your laptop of your own.
If you're really smart, you might be able to repair a broken keyboard, the headphone jack, or even the entire display. However, the SSD seems to be the easiest to achieve.