William, thank you for clarifying that for me! I guess I was looking at the frame incorrectly. Thanks for the response and easing my mind.

The frame depth of your new window is the same as the vast majority of others (most likely same as all others that you've considered). Your original window could have a more shallow depth that would mean the window will extend in or out farther than original. The superior way is to push it in. As he explained though, no way would it be 3", it's more likely to be an inch or less, give or take. If the original was a customary 3 1/4" jamb depth and not a super cheap builder window that is less, then it will be the same.

Back to the installation, how are they sizing the window? Same as original? Downsized to slide into the jamb return? With nail fin or without?

We are happy to offer insight and advice, but only your contractor can answer your question at the end of the day because there are a few different ways to install a window in your situation.

HomeSealed, our original windows seem to be pretty cheap builder grade, probably below average. I'm not sure how the installer is sizing the window. He probably told me but I don't remember. I do know he said the J channel doesn't get removed. He also said the window from the inside would extend further into the house about 1/2".

I think I was totally misunderstanding the window frame depth and how it fits in the opening and starting overthinking and panicking a bit. I will double check with the company that will do the install to confirm these questions you brought up but I feel pretty confident they will look totally fine.

Thanks very much for your response!

What state are you in ascolling?

Window Genius, we are in Indiana