No helper for me today so I had to devise a belt and suspender removal plan for taking out the windows. This is how I did it.
First step I used a small tool make for removing O-rings to pull out the putty tape all along the lower edge. It works great for hooking out the putty. This is a very inexpensive item available at auto parts stores and hardware stores. Photo below shows this small tool.
Photo below is of my beautiful assistant that volunteered to hold the window in place so it could not fall
while I continued to work on removing it.
Take some clamps and a piece of plywood around a foot or so high and clamp onto the belly band where the upper and lower halves are joined. Because it is hollow underneath you can get a clamps in there and over the edge of the wood. I added a soft foam block that was from packaging material between the wood and glass and put barely any pressure on the window. It is just a gap filler. A rolled up towel would also have worked just fine.
Next step is easy too. Go inside and remove the clamp ring. Remove any excess putty tape that might have squeezed out to the inside.
Next go back outside an pull out the rest of the putty tape. I don't have the arm strength to just yank the window out and I did not want to pry it out so I took my time and used the O-ring tool and pulled out the putty. Work from the bottom edge up towards the top center on each side and there will be no danger of the window falling out. I needed a step stool to stand on so I could reach the top edge so if you are vertically challenged have one handy.
Now if you feel you need to you can hold one hand against the window and remove the clamps with your other hand letting the plywood drop out of the way. Otherwise just use both hands and take the clamps off, the window likely is going no where since it is on an inward slant and will most likely have some pull on it from the small amounts of remaining putty tape.
Just pull on the upper edge of the frame and it will begin to come away from the shell. You can change hand position downwards as you work if needed. Hooray, you are done without needing a helper or a lot of physical strength
Every day try to do something you were afraid to do. That is pretty much the attitude it takes to face working on vintage trailer items such as windows. It is perfectly normal to worry about messing up so don't let it hold you back from getting your project done.