The joys of home ownership :)

You don't have to tear up the stucco. Here is a good method. Get a diamond blade for your circular saw. Get an expensive high quality one. On the outside, right NEXT to the exposed aluminum frame, cut through the stucco AND the nailing fin. Experiment with your blade depth because you don't want to be cutting into the stud. Diamond blades don't work so well on wood! Be careful on the corners to get a full cut - you'll have to go past 3/4" to compensate for the circular shape of the blade. When your finished, the old window will lift out if it doesn't fall out, so don't hold on to the window when your cutting. Also wear a mask because this is very dusty. At this point, you should end up with a clean cut in the stucco. You should measure your window to be app that size, and you can do that before cutting. Give yourself a minimum of an extra 1/4 inch all the way around for easy fitment between the stucco. You will most likely be behind the sheetrock at that point, but that's not for sure. Once you do one, you'll know how to do the others better. Worse case, you'll have to cut the stucco twice on the first one. DO NOT forget to flash/drip cap above the new window. You can get up in there with a sawzall blade and cut the nails to remove the upper fin, which should give you plenty of clearance for your drip cap. Go ahead and rip out your sheetrock before installing the new window, and then just jamb up to it once it's determined where it will sit. You won't loose much glass area, if any, if you do it this way.
The new window, in this situation, will stick out past the stucco app 3/8 of an inch. You will be able, hopefully, to put a nice neat bead of caulk around it that way, with no raw stucco edge showing. Be sure that you measure for this from the inside surface of the wall around the window all the way around, because stucco can be much much more uneven than the inside sheetrock.
Don't forget you can measure where the studs are by measuring between the sheetrock on the inside and adding for the thickness of the sheetrock. Compare this measurement with what you get measuring the exposed aluminum frame on the outside - BUT, use your inside stud to stud measurements for your basis of determining the new window size. Also, do not forget, window sizes are always width first. width x height. Always.

If this sounds like too much for you, bit the bullet and have the pros do it. If you don't know what you're doing it's not hard to butcher this kind of job. Worse worse case, you're patching stucco, but that will always have a tendency to crack where you patched it.
And please be careful with power tools on ladders. Always have a helper or two. Preferably one to steady the ladder, and one to hold the window. Tie off the ladder, tie off yourself.

I hope this makes sense to you. Good luck.

If this is the same post from the other board, it is EIFS so it shouldn't dust that much.

I would go with a cut back as I mentioned previously.

Ken,

Please forgive my brevity. I thought you were the same poster that had posted a question about EIFS.

The best way, in my opinion, is much like WindowDog mentioned.

I would cut back the stucco (wet down the area and where a mask as silica dust is very dangerous) and put in a new construction (i.e. flanged) window with new flashing, drip cap, and trim.

Thank you so much, WindowDog, for your thorough instructions. My husband is a very experienced handyman so this project should be easily doable.

Windowswashington, thank you for your tips as well. No problem. I don't know what EIFS so you're correct that it wasn't me who posted that question.

I really appreciate both of you taking the time to answer my questions. I started reading other threads on this forum. You two obviously have a wealth of knowledge about windows and have spent a lot of time helping others. I have other questions but I'll post them in a separate thread. Thanks again.

You have an experienced handy man in the house and you're ready to pay someone to replace that glass? try calling the glass place yourself and getting a price, you might be pleasantly surprised.