If you don't have any kits, get a full test kit (pH, ammonia, nitrite, nitrate). The API Master Freshwater kit is a good one.
If your fish start looking stressed at all before you've tested, do a 25-50% PWC
(dechlorinating and matching temperature of course!).
The bio-wheel (and filter media) should recolonize with bacteria eventually... but it will take some time I am guessing.
Familiarize yourself with the process of the nitrogen cycle so you know what you're looking for. You need to keep your ammonia and nitrite levels below .5ppm to be safe, preferably more like 0ppm (a cycled tank has 0ppm ammonia and nitrite and 10-40ppm nitrate; nitrate is removed through PWCs).