Power supply for Menards buildings

I am about to buy my first Menards building ,i know you are suppose to use their power supply for there buildings ,i did a search on the forum & it is a little confusing to me as far as what my options are available to use ,my first question is even if you use their power supply is ther an on-off switch with there power supply? ,second question is i want to have a switch just for this building at my control panel ,can i cut the cord & extend it to the length i need to reach the control panel assuming there is a switch already there ?, I found during my search that i can use an ac-to dc converter to hook up to my transformer & adjust the voltage to 4.5 volts ,is this an easier way for me to accomplish what i want to do ? Looking forward to doing this project .