Hello and Welcome to Fishlore!

Twirling disease cannot be treated. I am unsure of what causes it, but i know there is no cure.
You said they people at petsmart said that your ammonia and nitrates were high.
Ammonia is toxic to fish, at any level.
nitrate is "ok" for fish, in low concentrations (below 20ppm). I would Add some prime to your aquarium to detox your ammonia for the next 24hrs and do a 50% waterchange. This will lower the ammonia and let your tank finish the cycle.
Also, your Aquarium Info says that you do not know about the
nitrogen cycle. here is a link that will help you out with that:
http://www.fishlore.com/NitrogenCycle.htm
Also, we highly suggest to get a personal liquid
test kit. They are reliable, and cheaper in the long run.
One more question, what size is your aquarium?