re: Has anyone tried replacing house windows themselves?

I replaced mine a few years ago.

Pretty straight process if you have basic windows.
I used a hammer and a pry bar to remove the wood trim from around the old windows.

Most windows are standard sized so you can probably get them already made at Lowes, Home Depot...

Just make sure you have a little extra 'wiggle' room in your measurements or you will struggle mightily.