Put your hand on the top of the soil, you should have the stem between your middle and index finger, pick up the pot with the other hand and tip upside down, it should come right out. if you see lots of roots around the outside its time. If not, then maybe check your soil pH.

Doing this will not hurt the plant, just don't keep the roots exposed to light for more than a few minutes.

p.s. best to do this in the tub, it could get messy