I'm happy to report that the little mistake I made-- and the simple fix I came up with for it-- seem to have worked out perfectly fine. It didn't set in motion a horrible chain event of problems. In fact, I doubt I could even find it now, without counting many, many stitches.
I think the blanket is probably long enough now that I could just finish the row I'm on and go ahead and start on the edging. However, I may want just an extra row or two more to make sure it's long enough to stretch out on the couch with. No sense in stopping short when I already have the yarn (and no specific plans for any leftovers there might be).
I'll be so excited to finish this project. My first crocheted afghan! Back when I bought the yarn, I was planning to make a very simple blanket using strips made on a knitting loom. I mistakenly thought crochet would be too complicated or time-consuming for me. I'm so glad I finally learned at least the basics of crochet! Though I know you can do some very neat things with knitting looms, I think it's actually much easier (for me, at least) to do things with a crochet hook. It just feels more versatile and accessible.
When I do finish the afghan (tomorrow or the next day), I'll take some photos and measurements so I can update the Ravelry page (and this blog), and then I guess I'll give it its first gentle trip through the washing machine. (I'm a little nervous about that part. I'm sure it'll turn out fine, but still. . . All that time and effort going into the washer makes me a bit apprehensive. (g))