You need to be very careful with the ones on the side. They both thread into a floating nut plate that is only held to the inside of the frame with a small strip of metal folded over the center of it. The plate looks like a small dumbbell with a very short handle and the metal tab is about 1/8" wide that folds over the handle.
If you push on it and bend the tab, it will fall down inside the frame and is a real PITA to fish back up into place and you won't do it without removing the frame and drilling a hole in a convenient spot.
I can attest to the PITA-ness of that, it happened to me, I managed to use a piece of wire coat hanger and get it in to a bolt hole on the plate, maneuver it up into place (kinda), get about 2 threads started on the other hole, then get the other bolt started, there is no match to the sinking feeling you get when that little backing plate drops.
If you can, leave the upper bolts in but very very loose, tilt the windshield forward until the lower bolt hole in the frame is outside the hinge, then loosely put the bottom bolt in a few threads, this holds that plate in a place where you might not drop it, then take the top one out and replace the hinge, installing the new one do the reverse, one side at a time. Good luck.
Edit: it's been a long time since I did this, I may have that backward, you may need to tilt the top out of the hinge and leave the bottom in, it'll be pretty obvious which way works when you have them loose.