Can you get into the seam? I didn't know (or had forgotten), that little bead of plastic on the short end of the seam ripper has a use. Turn the ripper so that little bead is on the underside of what you want to open up, take a deep breath and start pushing it into the stitches. That little bead seems to guide the ripper. Clipped threads will collect in the ripper so take it out and remove those every few stitches. Good luck! (You might want to make a sample line of stitching to try this before working on your "good" piece so you understand and feel a little more confident in what you are doing? Otherwise that method of clipping every few stitches and pulling the thread on the other side works really well, too.)