The damage is minor. Exactly as you said about the vertical stab, bend the stab back and place some glue between the cracked sections. Get some straight pieces of balsa and clamp the stab to it to make sure it's flat and straight. Recover with monokote and some trim sheets.

I agree with Ken, fixing it is easier than replacing it.

Make it straight and correct. The avistar's a nice flying plane.

Jim