Bro I can tell you about Karachi and Peahawar as I know about markets in Karachi and Peshawar, cant say anything about rwp but yes In My Opinion it is very less likely for an Old Corolla's part not to be available in rwp or other cities.
And for power windows, you wont have to get the doors changed, the shop from where you'll get it installed, they'll make your normal windows to power windows on the same door i-e, by installing motor and buttons panel on the inner door's side. So no need to change the door.