Designing Kitchens and Bathrooms - Shower Doors

I currently have shower doors that fold not slide. The previous owners installed these themselves. They did a hack job and the caulk looks horrible. They also used screws into a fiberglass shower/tub to hold the doors in place. I want to take these awkward doors off and put a sliding glass door in. My question is how do I remove the old doors wihout destroying the shower. Also, If the door frame does not cover the holes, what can I do to fill the holes and have it not look like crap?

what you should do is remove the old doors by taking out the screws,then cut the caulk with utilty knife they should come right off, after you get them off take and scrape the rest of the caulk off, clean it with denatured alcohol, then install new track right over where the old one was, level and plum and your doors will look like they were there from the begining, Good Luck
Frank