I'd hose it down and look for the leak in order to know where to start. Are you sure it is not the rear side window(s)? I had one that leaked. Also check the area where the hinges attach to the body.
Assuming that it is the hatch that leaks (between the frame and the glass that is) it is possible to reseal it with the hatch on the car. Remove the trimmings first, the sides and rear are screwed in place and the front is clamped (push it forward gently, prying each lip forward from the underside a mm at a time as you don't wanna bend it). Now you remove whatever sealant you can get off of there, clean and reseal.