I finally found what appears to be a great tutorial for inserting an invisible zipper. AND it doesn’t require you to use those little plastic pieces that are supposed to form an “invisible zipper foot”, which makes me happy because I’m pretty sure there is no possible way to sew with those on my machine (Kenmore 19233). The tutorial is in the magazine Sew Stylish.
I got the magazine at Borders, but saw it at Joann’s, too.
I haven’t had the time to try the invisible zipper again, but now that I’ve got these instructions, I’m ready to go. My first (failed) attempt at invisible zippers was here.