Well you gotta fix the crack first.. right?
I took the vinyl top off of mine and it was in pretty decent shape. careful with the grinder when removing the little mounting nubs.. just enough to run them smooth.. don't press too hard. I used a metal filler in the seem after that I used a finishing coat of body filler. if you can't fix the rust, you gotta replace the portion that is rusted, rotted or cracked. I did it, but once again my base was pretty decent shape.. Those vinyl tops just love to soak up all those years of moisture.. I think the side windows are the same, but I had a set from a regular top, and they looked a little differnt.. so I used them. The rear finish moulding is trashed.. you will have to get it from a regular hard top.
When doing this job, remember to take your time with the finishing work, it is what you will see when getting in and out of the car, It's right at eye level.. good luck..