Replacement slider and hangers for mirrored bifold closet doors

In 1991 two closet Monarch bifold doors were installed, one closet has three bifolds, approx. 90 in. Wide and about 75 in tall; second door has 4 bifolds, approx. 120 in. Wide by 75 in tall. Tracks are installed. The top and bottom slides are "shot". No one locally seems to have replacements. One shop came up with a rube-Goldberg fix, hasn't lasted. So, are our door sets compatible with your newer slides? If so, how do we remove the doors to retrofit them?