I have to say, changing a screen in a door or window is not as challenging as I thought. I also saved a ton of money doing it myself. Home Depot and Lowes has complete kits that are not expensive with instructions.
The kits come with a roller to push the rubber gasket material into the channel around the screen and you buy the screen material on a roll and simply cut it with a scissor or razor knife.
You will need a straight edge to cut it accurately and I use a T-Square, a long steel ruler or a level and cut it over an old cardboard carton so I don’t cut into my floor or dull the razor blade.
Give it a try first on a small window and once you get the hang of it go to the door or larger window.