You can download the parts breakdown with illustrations here:
http://www.thetford.com/wp-content/u...0_20151105.pdf
Looking at page 8, item #7 is the hinge support bracket that holds the top hinge pin for the lower left door. It looks like the screws are accessible from the front without removing the upper door.
Dometic refrigerators have a center "double pin" hinge bracket and you must pull the refrigerator from the wall, remove the top hinge bracket, remove the freezer door and then you can access the hinge bracket for the top of the lower door. It doesn't look like that's a requirement on your Norcold.
Keep us posted on what you do and how you repair it. No doubt someone else will have the same question in a month or two.
Good Luck