Ok... (sigh) since this is my first tank and is now cycled, I would like to know the proper way to take care of the filter properly. I have a 28 gallon with a Top Fin 30 that seems to be doing its job

but its been almost two months and I started to ask myself questions like: When do I replace the filter media... HOW do i replace the filter media not to disturb the bacteria that COST ME SO MUCH TO ESTABLISH! I want to know how to do it and when to do it properly... in order to avoid any potential disaster!!
-Thanks- Alessa
Ps; is the top fin 30 enough for my tank?