I have a kenmore refrigerator freezer that freezes up on both sides I was going to replace the damper door and themostat but I don't know how to disconnected the water lines since I have a ice maker

What you are proposing replacing has nothing or little to do with your problem, unless the damper door is broken. When you replace the t-stat you have to make sure you put the capillary tube exactly like it was in the old one. That means the same length is exposed on new one and it is located just like the old one, too. Do not put in a t-stat unless it is not cycling when there is no ice build-up. Your real problem is the defrost system has something bad which could be: defrost timer, defrost thermostat, and defrost heater. Just replace it all and you should be okay, but you can test each part. The defrost heater and t-stat are on the freezer coils. You will have to totally thaw it out to work on it. You need to make sure you clean the condenser coils very well, too, or your compressor will burn up.
Here are some manuals: https://dl.dropbox.com/u/8010163/Whirlpool%20Refrigerators.zip