Your home is all block with a stone facade? if so your windows are set up for block frame constuction (I.E. no nailer fin like wood construction).
Do you have drywall inside? or just block?
If it's block then just measure the width and hight go to a trusted window company to order your windows for block frame, chances are your windows are not a standard size like the products at home depot or lowes.
Assuming the worst and you have drywall inside, you will need to remove the portion around the windows and pull them out from the inside.
Most windows for block homes are held in by small clips and caulked in place.
Another question do you have metal framed casements or aluminum windows or wood?
Metal framed you do not have to remove the sashes.
start buy cutting through the window frame and colapes the the frame out of the wall, you may have to pry a bit to get it out depending on your type of window.
after the old is out and you already have replacement handy time to install.
I personally don't use the clips I predrill the side jambs (2- 1/4" holes3-4" up and down) set my window into place (leved) and mark the hole location, pull window back out, drill block and install plasic or lead anchors.
reset the window and start 1 screw fixed side of window then the oppiset side( do not tighten them down all the way because you'll want to center the window in the opening.
tighten screws making shure that every thing stays square and plumb.
caulk around both sides( you may want to insulate the perimeter of the window depending on the gap you may or may not have, caution useing expanding foam, it tends to distort the frame if you use to much).
Now replace the drywall if needed.
Good luck, once you get started you'll see how really easy it is