Pozzi Double Hung Window

Hi,
I have a few of these double hung Pozzi windows from around 1999-2000 time frame that the balance assembles are no longer working and the windows sag or will not stay in position when opened. They are wooden interior and clad aluminum exterior and are about 6' height and 37 inches wide.

I am just checking to see if you are familiar with this style with the interior sides being about 3" wide piece of plastic that runs the entire length of the window and hiding all the mechanisms behind it, except you can see the springs are no longer attached to any thing from the pictures. I thought I would inquire before I started trying to remove the plastic liner to get to the actual parts on a good way to remove the liner. These windows open and close via a push in release on each of the top corners so it is not a compression style. Any advice would be welcomed. Thanks