Wiper arm mount question


I am trying to take all the windshield wiper system apart to clean and do a repaint.
Twice this happened......on the motor itself one of the three nuts started to just spin freely on the stud. IT is like the thread wore off or something and now I can't get the nut off.
So I stopped with that and decided to tackle getting the wiper arm assembly off(not the part that attaches to the motor, rather the part that attaches to the body). The Hanes manual just says to remove three nuts that hold it on. So I tried that and wouldn't you know it, it happened again. The nut spun freely and I cannot get it off.
So my question is: What is underneath that the arm bracket mounts to? I see three other bolts but I don't want to get into getting under the dash to repair it. If I was to cut the nut off, would I be able to get the mount out and replace it?



