I had to remove my toppers a few years ago when I replaced the awning rails with gutters. Easy job. Depending on the brand you can lock them in the extended position with a cotter pin or even a finishing nail. Once locked you can unbolt the hardware from the slide and then remove the other end out of the gutter/awning rail. Your best source of the procedures is You Tube.
If the wear is at the coach end there might be enough excess material on the roller end that can be unrolled and the reused. My slides are a bit shallow and there is probably enough material to effect repairs rather than replacing the material.
If you intend to replace the topper material rather than the high cost of going back to the OEM check with local boat cover shops or stick and brick patio awning manufactures. Using the original as a pattern getting replacements custom made locally can save you lots.