To modify parts you need to use an svg editor (the free one being Inkscape) to modify the svg files. Both it and parts creation have a fairly long learning curve though. Tutorials are here:
There is a stepper motor in core parts that will likely be close enough to what you have. The power supply I expect will be basically a box with two terminals and is easy enough to make. I’ll add the additional text in to the current part for the settings (I saw it, but was too lazy to add it.)