The seal comes out complete with the 4 pieces of beading holding the
bottom
panel in place. With a nice big chisel you should be able to pry the
beading
out (carefully) without marking it.

You'll have to remove either left+right or top+bottom beading first as
one
pair holds the other pair in.


I got the beads out but buggered if I could get them back. Those plastic
panels aren't cheap either, and the earlier, thinner type isn't easy to
get
hold of . I ended up getting a man in. £100 including the flap.