If I were you, I would not get a discus. As mentioned before, they are schooling fish and need company of its own species for the same reasons, say, a neon tetra does. Also, I highly recommend that you get a heavy metal filter (RO recommended) as the heavy metals can hurt these sensitive fish. I don't know how experienced you are (please do not get offended), but if you are just getting into the fish keeping world, I would suggest you wait on the discus. They are very sensitive and when they get sick, they are harder than many fish to get well again. They need VERY clean water, need to be in groups of six or so at the minimum, and should be kept in nothing less than a 55g or so. They are also very expensive (I paid $75 apiece for mine). Also, when it comes to rescuing, there are mixed opinions on this subject. I don't want to start a flame war, but in this case, since the conclusion that I draw is this is the first time your LFS got them in, I wouldn't rescue them. If you did, they might think they are selling and will bring more in. Many other fish will suffer because of this.
HTH,
Ryan