First, you have to remove the sliding panel and the stationary panel. The vast majority of doors out there have the sliding panel on the inside half of the track, and the stationary panel is on the outside. Whatever the case in your particular door, the outside panel has to come out first. To remove the fixed panel, you need to remove the sill cap that snaps into the bottom track and runs from the fixed panel to the side jamb where the sliding panel locks. Force a screwdriver into the crease and pry the cap up. Then, look for screws on the inside side jamb holding the fixed panel in place. These screws prevent someone from prying up the sill cap and pulling out the fixed panel in order to gain entry into the home. In addition to the side jamb, be sure to check across the top header and bottom track for screws there as well. Once all the screws have been removed, you need to pull the fixed panel away from the side jamb. You can start by simply grabbing the side rail of the fixed panel and pulling as hard as you can. If you’re lucky, the panel will pop free. Then you can lift the panel up as far as it will go into the top channel and swing the bottom away from the track, and remove the panel.
Now, I said “if you’re lucky”, because in most cases the panel will be stuck in the side jamb, the bottom track, or both. Usually, you’re going to have to use a pry bar to loosen the fixed panel before it will slide out of the side jamb. Once the fixed panel is out, removal of the sliding panel is usually easier. Just lift up and swing the bottom away from the track, then remove the panel. Sometimes the bottom rollers will prevent the bottom from swinging out of the track. If that’s the case, you will need to find the roller adjustment hole in the bottom corners of the sliding panel. Put a screwdriver into this hole and turn the screw counterclockwise to bring the roller as far up into the bottom of the sliding panel as possible. This should allow the slider to come out.
Now, you want to remove all the screws from the side jambs, top header, and bottom track. Then, take a pry bar and get it under the bottom track about in the center. Pry up until the track is separated from the floor. The next step will depend on whether your old frame is nailed to the house frame, or simply screwed in. If it’s screwed in, then the frame should now be loose in the opening, since you removed all of the screws. You just need to remove whatever inside trim there might be around the door frame. This type of frame should come out. If your door is nailed to the house frame, you will have to do a bit more work. Use a hacksaw to cut the track in half, approximately in the center. Start with either half and raise the cut piece up towards the side jamb until the track piece separates from the side jamb. Do the same thing to the other half.
So, now you have to remove the side jambs. You want to do this without damaging the exterior material that surrounds the door frame. Take a heavy chisel and pound it into the crack between the frame and exterior material, whether it’s stucco, siding, etc. Start at the bottom 6 inches first. What you are trying to do is pull the nail fin away from the nails holding it in place. So, once the chisel is pounded through the metal frame, pry away from the side wall. The heavier and longer the chisel, the more leverage you will have. You will hear the frame “pop” free of the nail. There will be several nails holding each jamb in place, so you want to start at the bottom and work your way to the top corner. Once you get the bottom third loose, many times you can grab the jamb with both hands and pull the rest of the nails free as you go up. When you get to the top corner, work the jamb free. Do both jambs, then do the top. Sometimes the top has no nails, or just one in the center, so it will come down pretty easily. Be sure to wear safety glasses and a dust mask when doing this job, especially when removing the top header.