Since you can get into the car, you will have to remove the door trim panel on the driver's door, the handle and trim from outside, remove the retainer and linkage from the lock cylinder and pop it out of the door. But, before you do that, try some powdered graphite into the key slot. Does the key go in at all? If you look at the lock, there is a little metal plate on the inside that closes over the opening when the key is not in there. Can you see that? If you can't see it or it doesn't move, then it has broken and is jamming the track for the key.
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.