I'm assuming your bus is one of the smaller ones, like 4 windows, and you wanted it that way?
I'm just wondering how committed you are to this specific vehicle? There are plenty of 4 and 5 window buses with 5' 10" of headroom to start out, and that saves you from what is really a big project!
A roof raise is generally only over the passenger area, with a transition right behind the driver's seat(more or less). The transition itself is the hardest part, requiring good metal fabrication skills. It can certainly be done by a first timer, but only if you're good at cutting, measuring, and welding light gauge steel.
At 5'4, I'd buy one of the many buses that are already a good match for your body
"Reality is that which, when you stop believing in it, doesn't go away" - Phillip K. Dick