Jason

Silas313
I wouldn't add any ammonia to the tank while you have fish in there. Adding ammonia is only for cycling your tank without fish. I am currently cycling another tank right now and its going on 3 1/2 weeks, and it's still not done yet. However if you cycle a tank without fish in the future, adding ammonia is then required. I went to Walgreens, Pick-n-save, Home Depot, and Walmart and all of their ammonia had additives to it. I finnally found "ROOTO" Ammonia at True Value Hardware store.
As far as the test strips go, they are crap. You will want the test kits with the test tubes and little bottles (reagents). I have bought the Hagen kind before and was very dissapointed. The shades of the same color were very close, too close to distinguish. I now buy the AQUARIUM PHARMACEUTICALS, INC. test kits because these are the easiest for me, they actually have different colors. I would buy the ammonia, nitrite, nitrate, and maybe PH test kits. IMHO a master test kit is unnecessary, I can't tell you the last time I tested my General Hardness or Phosphates.
As far as I THINK, your problem is that your tank isn't cycled properly and possibly overstocked. I wouldn't change the filter because that is where your bacteria colony is forming, along with in your gravel. If your filter is clogged, then rinse it out just enough to unclog it.
I would just ride it out and hopefully the fish can survive. I would do water changes every other day like OneEyedTetra said and also add some CYCLE to it. If you buy anything to help at this time CYCLE would be it. And, if and when you vaccuum your gravel, do not vaccuum all the gravel at once, do a half or even a third at one time.
Hope this helps. Good luck with your fish!