First of all plan on it being there awhile. After mine was just returned (7 weeks from the time they got it) and they missed one of my repairs as they did not read the letter I wrote I would recomend you keep it very simple. Don't go on and on as they are not going to read it all anyway.
Just tell them in a couple of sentences what is wrong and let it go at that.
Just tell them in a couple of sentences what is wrong and let it go at that.