Mine came apart fairly easily. I just unscrewed the bottom from the sides. My angled threaded pieces that hold the screws were rusted beyond help so I had to make new ones and THAT took a few tries to get them correct.
There are 8 screws holding the frame together (after you remove the side posts) The go into an "L" shaped metal piece which is most likely rusted solid. So when the screws break, plan on making a couple of new metal brackets. They are just 1/8 x 1/2" steel but bent greater than 90* and tapped 10/32 with really short screws. I did it by trial and error and it took a few hours but do make sure you fit each side bracket and snug up the screws BEFORE the glass goes in, too long a screw and you bought a new glass. Not quite right angles on the brackets and the corners will not meet.
You will need a vise, drill, and a 10/32 tap.