Heh, I work for safelite autoglass. If your mustang is not a fox, you need to take off your a-pillar covers, then cold cut the top and 2 sides, then use a long knife (razor knife with long handle) to do the bottom. If it is a fox, the cowl and all the metal trim needs to come off, then you can cold cut the whole thing.
OR you could just pay like 75 bucks to have a glass guy do it, usually much safer.
Take all the trim off, be careful with the top and sides trim. I gently pried them off with a small prybar. Put a piece cardboard between the prybar and glass when you do this step. I bought a windshield removal tool from harbour freight tools for 7 bucks. It has a right angle blade at the end of it and a cable and pull handle at base of it so you can guide it around the windshield. It was very easy with this tool and only took me about an hour and a half. This was the first time I ever pulled any glass. Hope this helps.