I would purchase test kits yourself as your lfs
person doesn't seem helpful in the slightest. I wouldn't adjust anything until you know what you are adjusting specifically. Has the tank cycled thoroughly? Here are some test kits for you to consider:
Hagen: I've always had good luck so throwing that in the pot as well.
Tests to purchase: NH3
(cycling purposes), NO3
, pH, Calcium, and Alkalinity.
Various websites make these available, here is an example: http://www.marinedepot.com/ps_AquariumPage~PageAlias~test_kits__index.html