Can't help you with Kranz, but some general tips:
-make the letter short. If it goes past one page you will seem like a kook.
-be polite. Do not be a fawning fanboy. Write it as professionally as possible, as in "I have been an admirer of your work" or "I want to thank you for what you did... it was inspirational to me growing up..." Something like that. Don't drool, don't be obsequious, don't ask for personal favors.
-if you are going to provide a photo for him to sign, also provide a stamped, self-addressed envelope so that he can mail it back without having to pay postage or find an envelope or whatever. (And if you're going through all that trouble, include some cardboard to keep it stiff and write "Do Not Bend" on the outside.)
-Don't write anything embarrassing. Nobody wants to know about your health problems or your pain and suffering.
-keep it simple. Write the intro, make your statement, end it.