The rough framing for a slider will completely replace the framing for the window. The approach taken will be different for a structural support wall, or non-support wall. The changes will involve completely removing the studs and sill plate where the opening is to be created, and installation of new studs (doubled if support wall), jack studs and a header sized for the span and load. For a support wall, the ceiling joists (or second story joists) must be supported while the framing is replaced.

Framing is standard except for header size and load transfer through single or doubled studs and jack studs at each end of the header. This may be a code enforceable size in your area, (permit required?). Once the rough frame is complete, and sized according to the rough opening specifications for your door (included in packing) actual installation is fairly easy.

This link shows the entire process of replacing a window with a slider. Good luck.

http://www.hammerzone.com/archives/framecarp/slider/roughopn.html

replacing window with sliding glass door