You should be able to access the water reservoir by taking the crisper drawers out. If you still can't see them you may have to take the back cover out. It is shown in this diagram of your fresh food section. Part 810.
Replacement parts for GE TFX28PBDAWW | AppliancePartsPros.com
As for your second question, you can also see the filter parts on the same diagram. Hope it helps.