Originally Posted by stovalini69
how hard is it to replace and how much does it cost to do this.
It's a pain to replace. I know that for the foxes, it requires removal of the dash. Yup. That's right. The entire dash. I really have no idea how much a shop would charge you to swap one out.
Whatever you do... don't buy a cheap Autozone-ish heater core for a replacement. Go to Ford and get the factory part. This isn't something you're gonna want to do again.
Here's a link that shows how to swap one out on a '86 GT: 5.0 Stangs - Late Model Mustang Restoration Specialists