The noise is your door latch actuator. The park costs about $150 from a Jeep dealer. I am not sure what they would charge you for labor but I would guess another couple of hundred bucks. I just replaced mine on a 2004 Liberty and I think it is pretty similar to the 2003. I am medium handy but it was not the easiest fix. Here is what I did
First get the part.
Order a set of door trim tools from Harbor Freight. This is a set of 5 blue plastic pieces that slip easily under your door trim panel and allow you to pop off the inside panel without scratching or damaging anything. Don't use a screwdriver. I think about 10 bucks for the set
Pick a nice sunny day with lots of light. Take a deep breath. Bring a chair to sit on.
Remove the phillips screw on the bottom of the arm rest. Pop off the screw cover behind the inside door handle and remove that screw. Now, I like to start on the bottom right of the door panel... slip one of your trim tools under the door trim and slide it along until you hit a connector and pop it out..use the tool and the door for leverage and in a sharp motion pop out the connector. Do that slowly all around the door. If you break one connector it is not the end of the world. You will have to buy one from the dealer. They are available mail order but you have to buy a bag of like 20... You may want to pick up a couple at the dealer when you get your part. I broke one.
So now all the connectors are popped. Lift the door over the locking knob. The door is open and locked before you start. Now holding the door...remove the door lock and the power window controls. You have two choices. Remove the wires leading to the controls or remove the control and all from the door panel. I prefer the latter because I am always afraid I will rip the wires out of the control. The controls are in place with little plastic nubs on the sides of the control. With a thin screwdriver push the little wall holding the controls in place away from the nubs and lift out the control. Now the door handle rod is left and it is connected by a plastic connector. Swing the plastic connector off the rod and pull the end of the rod out of the hole in the plastic connector. Take note of what you are doing. That is what you are going to be doing by feel alone in a little while. The door now is totally disconnected and can be removed and put to one side.
Have a beer. Don't let your wife see what you have done so far..she will scream....
Now starting in the upper left peel back the white plastic covering. It is held in place with rubber goopy stuff. Peel around the edges the left half of the interior door panel is exposed.
There is the opening you will need to use to get the part out and in.
Get a good flashlight. First remove the orange snap from the rod end.