Oh man, last part! The side pillows are probably the easiest, just because they're tiny. I deconstructed the old side pillow covers, to reuse the cording and zippers, and to use the pieces as a pattern for the new fabric. 2 zippers, 2 bits of cording, and the side panels for the pillows.














Covering the cording is pretty straightforward: wrap a 1.5" wide strip of cloth around the cording tightly (right-side-out for once), and stitch it up. I might be mistaken, but I think it's advised to use a special foot for sewing things like zippers and cording. Since my sewing machine is an awesome old 1970s hand-me-down from my former landlady, it doesn't have all the fancy attachments, so I just did it with a foot ordinaire, and it turned out fine:














Cut out two panels per pillow, slightly larger than the pillow itself:














Since there are no edge-panels for these, to accommodate for the pillow's shape, cut a 2-inch slit diagonally inward from each corner, and stitch it together like so:














Putting it all together with the cording is only slightly tricky. Same basic concept as all the others: pin it all together, inside-out and tightly. Working with the cording, you have to feel at it the whole time, to make sure the cord-part of the cording is lined up straight on the seam you're trying to sew. I'll try to illustrate it with a few pictures, maybe it will be more understandable:
If you look closely, you can see that the cording is facing the inside, sandwiched between the two side panels of fabric.











Being stitched up.













Below is the mostly-finished side pillow cover. To accommodate for the zippers on the bottom, hem the bottom edge of the panels:














The couch, in all its glory:














I'm pretty pleased. Notice the attempt at aligning all the patterns across the component pieces. There's only one really badly matched part: it's discontinuous across the left and right seat covers. I definitely had enough fabric to do it correctly, but I took leave of my senses when I was cutting it out.
Secret: it's still not finished-finished. I haven't added the zippers to the bottom of the side pillows yet, mostly because I hate sewing zippers and was in a hurry to finally have a finished-looking project. I'm also going to make the little arm-covers out of the leftover fabric, because the left arm gets a lot of sitting, and I would like to keep it as clean as possible. I probably won't bother posting the how-to for the arm covers, because it's pretty much the easiest thing (next to a handkerchief) you could make.