You might be able to trade it in at a local fish store, but if it IS a common plec, be prepared for them to say no. There is not much demand for these fish now, not only because they get so large, but also because there are so many much more decorative species around that are nicer to have.
You might try a Kijiji ad or Craigslist, likely you would have to offer it free to a good home, I doubt many will pay much for a common plec.
If all else fails and you cannot rehome it, don't release it. Euthanize it, if that's the only choice left, rather than turn it loose and hope for the best.
Edit- if you decide to get Otos, they need a group of their own kind to do well. Six or so is best, and they are highly prone to dying within the first weeks, up to the first two months. It is due to the way they are caught and starved, which kills off the gut bacteria they rely on to digest their algae based diet. Lovely fish, I'm very, very fond of them but best to be aware of the issues.
If you buy them, they should have been in the store for no less than a week, preferably two weeks, and buy the ones you see eating the food in the store if at all possible. They sometimes don't take to man made food, it is so very different from what they were eating before they were caught. They are all wild caught, unless you are very lucky to run across some locally tank bred specimens, in which case buy them, they'll be great.