Cheek implants can be removed under local anesthesia or under IV sedation depending on the patient's tolerance. A small incision will be made just underneath your upper lip where it meets your gum. It should not be painful. Since it has been few years, there will be small pockets, but with time these should collapse. You may also have a ring of calcium deposit or scar tissue surrounding the implant. These should gradually go away. Your face will be flatter than when you had the implants in your cheeks. After few months, you might want to consider having fillers to the area for more volume.
It is unusual for them to be painful. If they have been in that long and they are removed, your cheek may sag. Something can usually be done to help this depending on each person's situation. Insurance usually will not cover it unless there is an infection or medical reason.
You didn't mention the exact size of the implant, and that would be helpful. At 25, the tissue may shrink back fairly quickly. At 50, you may have a bit of sagging and may warrant a short scar incision facelift, as well as, some type of cheek volumizer (Perlane/Voluma/Juvederm Ultra) to give you back your cheeks. It is hard to give you exact advice without seeing you or seeing photos of you.
Like taking feathers out of a pillow, your cheeks will definitely SAG when the implants are removed. They need to be removed through an incision, much the same as their insertion. Do you have any cheek numbness? What about your upper teeth?