How to remove already installed laminate panel in cabinet?
Cut through particle board panels as far as you can with jig saw. Most likely they are not attached in the back.  The remaining 1-2 inches of the panel may be easy to break apart. If not finish cutting through with small hand saw. When 2 halves are separated pry each straight back from side panel to disengage the dowels .
On the top panel if you don't have space to run jig saw flip the saw over and cut through from bottom of shelf panel.