Fixing windows that won't stay open --- I know you posted the name of the window, but I'd have to see it. I have windows with the same problem. After examining it and having another window to steal parts from, I decided that the stick method will have to do.
Replacing windows with wooden siding. I've done this. It took me one full day with replacing the siding. Mind you I have always worked in an office and was not handy prior to the hurricane. You can do it. I've already posted a picture of this. Check out the early postings.
1. Have your new window bought. Buy flashing tape, shims, silcone caulk and nails or screws. Flashing tape has a tar like substance on the back and silver stuff on the front.
2. Look at this youtube video. It's good and explains flashing and installation.
I didn't do the sill pan. The window is inside the entryway of our home, and there wasn't one to being with. I noticed your window is really exposed so I'd would put a sill pan in.
3. Remove the wooden casing around the window.
4. The diagonal wooden siding may be right up to the window. If it is, you'll have to cut it with a skill saw, or remove the siding boards/panel and replace. I replaced our because of wood rot and further damage because of the flooding.
5. Remove the screws or nails that are in the metal flange of the window. I was amazed that our window was nailed with every few nails and they were short. It was a 36" X 72". Have someone on both sides of the window and take it out of the frame.
6. Put the window in as described in the youtube video.
7. Replace the siding or just the wooden casing/trim around your window.
You can do it! Good luck.