Uninstalling SheepShaver isn't hard.
First, do you remember where you created the hard disk file for Mac OS 9 to run on (if any)? That file gets deleted. Also, SheepShaver creates a couple of files in your home folder that are hidden: .sheepshaver_prefs and .sheepshaver_nvram. Both of these can easily be removed with the Terminal, if they exist. Finally, the SheepShaver and SheepShaverGUI apps get sent to the trash.