You may be able to trade them with another species at the pet store where you bought them. Just explain that you didn't realize that two convicts can't be kept in a 20 gallon tank and don't want the poor little guys to suffer. If the fish store is decent, they should be willing to trade you. Especially if you trade down (as in, you're losing money in the trade...but to have a better fit for the tank is more important in the long run).
Sorry you didn't get answers right away. The people here are really helpful though, so it's worth the wait you sometimes have to endur to get answers/suggestions.
I'm sorry the initial fish died, but it does give you a chance to "start over"! Invest in a test kit if you don't already have one, and check out the parameters before you add fish (i.e. change the fish you have). You said you're a newbie...so a good place to start might be to read up on tank cycling which will give you a basic feel for water chemistry and how fish and plants affect one another in a closed system (i.e. in a tank as opposed to a river). This is just my opinion, but I feel that including a moderate amount of plants in your tank is a good idea, especially when the tank is small. You don't need to go all out and buy super-lamps and carbon dioxide - just check out Byron's tanks he has a bunch of planted tanks with no added CO2. My experience has been that a planted tank is more "stable" than one without plants because the plants convert some of the bast sutff (ammonia, nitrates) into not-so-bad stuff for your fish. You still have to do water changes, especially if you have a large number of fish (because the plants only convert so much ammonia and nitrates).
Another suggestion I have is two stick with fish that stay small and are what are known as "peaceful community fish". These include tetras, corydoras catfish, rasboras, danios, some gouramis (but some get quite large), livebearers (eg. guppies, mollies, platies) and others I'm probably missing as well. Any kind of fish with a territorial streak in a tank that small could spell chaos for you, unless he's buy himself. For example, you could probably keep a school of tetras (pretty much any kind) and a 4-6 corydoras in a planted tank of that size without a problem. If you want big, territorial fish (that means most cichlids), you're going to need to invest in a bigger tank.
Wow that was a mouthful. Someone chime in to correct me if any of this is wrong...I don't consider myself an expert, just an enthusiast, and I often rely on the knowledge of others on the forum, especially Byron (because he's the most active low-tech planted tank guru on this forum I think).
I hope some of this helps, and I hope we can change your opinion about the forum.
Please keep us posted on what you decide to do.