If your current power supplies work with your motors and Gecko drivers, then keep them. Yes, the 126/107 takes 120/240VAC directly.
For the +5V for the SS, you might be able to tap off the PC's 5V supply if you want to make your own adapter cable, or just buy a wall wart style 5V supply. Be aware that many of the 5V supplies with USB connectors that are made for the RaspberryPi and the like actually output a bit more than 5V (I've seen them spec'd at 5.25V, which is 5V + 5% but he actual voltage may depend on how much current the SS draws). Check the SS documentation to see what the real max input voltage it.
As for links, there is a recent thread about someone else upgrading from the SoundLogic boards to a 126/107 combo. Not sure how much of that applies since in the other thread we were trying to keep as much of the existing Mach3 configuration as possible. And that setup uses 2 parallel ports. Using a SS adds another layer of configuration complexity (disclaimer - I haven't worked with a SS for over 5 years, so things may have gotten easier).