Hi Donny, instead of worrying about getting more discus I think you would be better off doing some research on basic discus care. The shop keeper gave you some poor advice regarding water changes. I would suggest starting with this video located in the first post of this thread http://forum.simplydiscus.com/showth...CH-THIS-VIDEO!.
Also read some of the stickie threads in the beginner section. Focus on how to do water changes, aging water, feeding and very important, how to quarantine new fish. Your best bet with the guppies and mollies is to put them in a different tank as I know that guppies need their water in the seventies and perhaps the mollies too. The rest of the fish are ok.
Pat