You can't really replace the soft top without the frame on the car. You need the frame fitted to get the top set up correctly.
The fabric is one layer. There is no internal and external layer.
When you buy the soft top it should come with the straps, wires and screws that are required to set the top up properly. But it would pay to check!!
Doing the soft top yourself isn't too difficult, but it really pays to have an extra pair of hands.