In removing the bed liner to clean underneath it, the only obstacle is those two tabs at the front of the box, in that I need to be able to spring them forward, so I can lift it up, but don't seem to have enough clearance to do so?

Any, thoughts, ideas, or suggestions?

 

Pulling the bedliner is almost a two person job because of this very reason. You have to lift up the center of the bedliner so that it basically folds outwards, and that should release the two pegs at the front. You can try using a long board and use it to push the bedliner up, and then put some weight on it to keep it raised. Then walk around to each side and try to free the posts without damaging the thin sheetmetal on the bedside seam.