tips on removing rear bumper cover?- 03 Camry?

There's an energy absorbing foam core behind the plastic covering that would not pop back. Generally, you just unfasten the screws and plates top and bottom to remove the cover. Not sure about '03, but most aftermarket repair manuals show an exploded view with location of fasteners. If you're going to be working on the car, always a good idea to have the factory service manual which would contain more detailed instructions, or more illustrations of related parts. A body shop owner could show you if asked the right way. A painless dent repair place or suction cup based tool could pull it out if you just want cosmetic repair with the dented foam behind.