You may or may not need to remove the rear fender to access the bolts on the silencer.
1) Remove rear fender if necessary.
2) Undo the bolts (usually 2) holding silencer to subframe.
3) Pull out old silencer.
4) Repeat steps in reverse to install new silencer. You may need to use high temp (RTN) silicone to seal the joint between the silencer and pipe.
It is as easy as it gets. Remove the two bolts that hold the silencer to the subframe and slide it back and off the pipe and then slide your new silencer on and reinstall the two bolts. I have used high temp RTV to seal the connection on some motorcycles but my SX has a good seal without it.