Removing/Installing Windows In Stucco in South Florida

Hello all, it's really nice to find this forum. I'm all about educating myself on jobs so I can do it myself and not need to pay someone else.

I'm remodeling a small bathroom for my first time and would like to change the old aluminum window out with an impact window. I don't need a permit if I don't change the structure, so I don't plan on cutting stucco/flashing/patching and everything is already demo'd from the inside.

From what I've studied, I can either cut along the outside perimeter where aluminum meets the stucco edge (leaving nailing fin in stucco) or I can try to collapse the frame and the nail fin should rip through the nails. Is anyone familiar with South Florida block homes built 1990 and if the nail fin is actually nailed or mortared?

I bought a 36" x 25" Jeld-Wen that should fit but the Florida Flange is kinda confusing. I assume once the old window is out I'd build a 3/4" frame around the rough opening for the flange to caulk to, add shims and use 3" Tapcons to screw to the inside block. Does this sound about right?

First 2 pics are of window to replace, 3rd pic is an impact window a contractor replaced somehow without removing stucco, and 4th is what the 3/4" Florida flange on the window looks like. Thanks in advance!