Most window replacement in Fort Myers is one of three things. Single pane aluminum from before the code changed, double pane units where the seal has failed and the glass has fogged, or vinyl that has warped enough that the sash no longer closes square.
All three are replaced the same way, and all three are a permitted job in Lee County. Anyone who tells you a straight swap does not need a permit is telling you something that causes a problem when you sell.
The surprises live behind the old frame. A sound block opening is straightforward. Rot or a bad previous install adds work, which is why we look before we quote rather than after.