A few pics of the steps involved in repairing the
infamous landing gear block on the Hangar 9
P-51 Mustang PTS.  This particular incident is
on the right wing.
Cut and peel the covering from the damaged
site.
In this case, there was some damage
caused by the gear/gear block shifting on
impact.  Remove the damaged pieces.
In cases like this, it's best to cleanly remove
some of the balsa sheeting around the
damaged area for easier re-sheeting.
Remove the gear block and sand the area
where it was mounted, as well as the block
itself.
Once clean, use PLENTY of 30 minute epoxy
to glue the block back in place.  Test fit the
gear before allowing to set, then remove the
gear and secure the block in place until the
epoxy is hard enough to hold the block in
place.  Then add a small block of balsa/light
ply next to the LG block for re-enforcement
(not pictured).  Epoxy in place with 30 minute
epoxy.
Once all of the broken pieces inside the wing
have been repaired, re-sheet the area with
1/8" balsa, then repair the covering in your
preferred method.  This is not the best
looking repair job, and can be done more
professional looking by a more experienced
modeler.  Regardless of how it looks, this
repair holds together well.  The student that
owns this plane soloed on it the very next day
after this repair was completed..