If you want to use reflector on the c# code that is called when someone executes a SharePoint Powershell command, you’ll be searching for the microsoft.office.powershell.dll.
You will not find this dll in the 14 rootfolder, because appearantly it only exists in the Global Assembly Cache!
While in reflector, press File > Open and type “C:\Windows\assembly\GAC_MSIL\Microsoft.SharePoint.PowerShell\” .
Here you’ll find the assembly you were searching for!
hope this helps,