The ice maker supply line is pretty easy to replace. It originates (as Jim A said) in the service compartment (where your water, tank drains & electric hookups are located) behind the removable panel. If you didn't know there was a removable panel there, it is right above the tank drain valves and is attached only with velcro fasteners and is easily removed. There is a puncture valve there that the small 1/4 inch plastic ltubing is attached to. Just turn the little knob clock-wise until it stops to turn off the water flow. If you want to replace the tubing, you can purchase the 1/4" plastic line at any home repair store (Home Depot, Lowes, Ace, etc.) pretty cheaply. There are really only two challenges in replacing the hose. Getting the replacement through the hole where it goes from the refrigerator compartment and on into the storage tank bay. Then routing it across the top of the upper holding tank from the passenger side to the driver's side where the valve is located. You have to remove the 2 screws/bolts that hold the holding tank bay door closed (there are two brackets on the under side of the panel that have bolts through them to secure the door in place) and then it will raise up like the other bay doors do. It just doesn't have the struts to hold it in place while it is open. You can use anything (I happen to use a rake with a long handle) to hold the door open while working in the bay. Now, what I did first, was to remove the tubing from the rear of the refer compartment and then get the new hose through to the storage tank bay. Then, I taped the new hose end to the end of the old hose and pulled it from the driver's side until the new hose appeared on that side. Then I removed the old hose from the valve and installed the new one. You will need a new compression nut when installing the new hose to the valve which is also readily available at any home repair store. Now, before you try to use the ice maker, you may want to strongly consider replacing the supply line from the solenoid to the ice maker. As wa8yxm stated, the tubing from the solenoid to the ice maker is paired with a heat tape to keep it from freezing in the wintertime and this combination usually results in the plastic tubing deteriorating or in my case "disintegrating". In order to replace this tubing, it is necessary to remove the refer from the cabinet to get to the back of the unit to replace the tubing. I think this must be what Paul Everet's wants $715 to do - that is, replace all the tubing from supply valve to the ice maker. Otherwise, it would be a quick and easy and inexpensive fix.
Now, if you don't use and never intend to use the ice maker in your refer, just turn off the valve and forget it and don't worry about replacing any of the tubing.
Roger & Diana
'03 Alpine 36MDDS