I've replaced a couple of Grob canopies, but it has been over 10 years
ago. Each went like this -

Tools -
Air powered die grinder with sanding disks and cutoff wheel
Screwdriver
Foil tape
Plastic drill and countersink
Small paint gun


Day one -
With the frame in place on the glider I used the grinder with sanding
disk and removed the gel where it contacts the frame. Cut off the
remaining canopy next to the frame with a cutoff wheel. (I once saw a
Grob mech beat one off with a hammer.) Chiseled and ground off all
plastic and the resin used to bond it to the frame. Grob uses small
screws to hold it place while the resin cures. Ground those off also.
(Approx 4 hours)

Day two-
The canopy comes oversize. Placed it on the still in place frame and
adjusted its position while overlapped and taped in place with clear
tape. Ran the cutoff wheel around and used the frame edge as a guide
removing all excess. Taped again in place. Drilled and countersinked
holes for small brass screws using a drill modified for plastic
(careful here or you'll break it). Removed canopy and put a bead of
resin on the frame. Pealed back the protective plastic around the
edge. Put it back on and lightly (real lightly) screwed it down.
(Approx 4 hours)

Day three-
Masked off at the level of the frame with metal foil tape. Hand
sanded the canopy edge to roughen and remove the resin squeeze-out.
Filled the gaps and screw heads with white Bondo and block sanded
level. Shot on gel coat with a touchup gun. After it cured, sanded
and polished the gel. Removed all the tape and protective plastic.
Cleaned and waxed it. Signed off the work in the log. (Approx 6
hours)

The moral(s) of the story is that it's not a huge task, break it and
you'll buy another, and these are hand built aircraft. The frame from
one probably won't fit another. Leave the frame in place while you
change the glass and it will fit like the original. Most of all, this
is how I did it. What you do is at your own risk. ;-)