Doors and Windows - Replace a window stool?

Hi,
I have two doublehung Pella replacement windows. I'm really unhappy with the original window stools. One is severely dried out from years of rain & sun. Apparently, It was left open all the time, & the elements have gotten to it. It looks like pine. The other one looks like it was just a piece of pine 1x4 just nailed in to finish the job. It doesn't even have an apron.

Is it difficult to replace the stool without taking the replacement windows out? The bottom inside of the Pellas butt up against the stool and are ?? flush/level?? with it. What trim pieces would I need to remove? Is there a sequence to follow?

TIA

Joe

As long as the windows are just butted to the stool and not actually sitting on it, you should be able to replace the stool without having to remove the window. Exactly which trim pieces you might have to remove depends on how the trim was installed, and which pieces may have the stool captured.