It took about 15 minutes. Very easy. I am pretty decent with tools - by no mean a professional but I am comfortable with a drill and a saw and a hammer. Anyway, I followed the directions in the Jennair manual, which I found online. Only thing they don't say is that you need to remove the two silver plates that cover the hinge opening before you pull out the door. Here was step by step:
~ Open the oven door
~ remove the two silver plates that are on the oven frame and keep the hinges from falling out (1 screw each)
~ gently lift the door out
~ lay the door on a flat surface exterior side facing down. Ideally, use a table so the oven handle can hang off the side of the table, allowing the door to lie flat.
~ remove 3 screws on top of door and two on bottom
~ pop off the frame (easy - comes right off)
~ There is a black steel metal plate running along the base of the oven. It has two additional screws that go into the hinges. Remove it.
~ you can now replace the hinges. Gently slip them out. Slip the new ones back in.
~ Reverse everything.
~ one thing I didn't realize immediately is that the new hinges have small steel "bolts" (not really bolts because they don't have threads, but i forget the term for them) that keep the door from closing all the way. Remove them.
total time was 15-20 minutes.