You can call Petco/Petsmart and just see if they can take your loaches for you, tell them you don't have room and that you got them off someone who didn't know better either. If they say no, that's fine. I know some people list theirs up on Craigslist, although a lot of people are apprehensive in doing so.
Glad you found a home for them! And they do yes, by the betta's in Petco/Petsmart they have heaters there specifically for smaller tanks but I've heard they suck, I have a 5 gallon heater in mine that i've used for a year or so, and a thermometer which lets me know that it doesn't fluctuate or overheat.