remind me is the rear hatch on the 02 an auto closing mechanism similar to the 07? If not, there may be some hope without going to a dealer. the pressure placed by the added strings must be preventing it opening. I suggest having two strong people press on the rear hatch and shoot some compressed air into the lock area. perhaps they will move around. you could use compressed water with a potentially similar result. you may have to try a few times. the other idea is to pour some fluid which will eat away at the remaining strings but leave metal unharmed.....