permits differ with each state, in my state, you would not need a permit because you are not increasing your living space or building a deck.
But, that does not mean that you don't need one. But, I am sure with this that you won't.
Load bearing walls are something to be very sure about and to make sure you know what you are doing.
Go up into the attic above the area to be worked on. Look at the directions of the ceiling joists. If your 3 foot wall is "perpendicular" to the joists, the wall is load bearing. If the wall is parallel to the joists, the wall is not load bearing.
If you do not have an attic space, get a cheap stud finder and mark the studs in the ceiling above the area and then make your assumption.