BaydeNoc

I would appreciate it if someone could give me some details on how to replace the sash balancers on a Anderson Perma-shield Narrowline double hung window. The bay window is over 30 years old, several cords have broken, and the rest wind up in jerks and starts. I see where the lower left jamb appears removable, but how do you accomplish with the sashes down, and the tension on the cords? Thanks