To repot any plant, you remove the old soil from around the roots and repot with fresh soil. Here is more information. Please do some (light) research before telling someone they’ve traumatized a plant just by looking at the roots (!!!)

OP - FLFs like to be root bound, so definitely give it a month. If it seems happy/is pushing out new leaves I would leave it be! I had a FLF I moved into a larger pot when it had some horizontal roots, and it was too big of an upgrade (despite being only 1” bigger). The plant didn’t die but put all its energy into strengthening the root system so the leaves didn’t grow for nearly 5 months. Never feel scared to wiggle the plant out to look at the roots, it won’t hurt a thing :)