Valve stem seal question?
yes valve stem seals can be replaced with head on, requires cam removal and cil. pressurised with air to hold valves in place whike vakve spring is removed seal changed and spring and keepers reinstalled. If you already had this done and it still smokes chances are you have a bad valve guide.
Yes, you can. There's an excellent article that gives you pretty thorough instructions on how to do that in the link below. Note: If this doesn't stop the smoking check and replace your Cam Position Sensor O-ring, that can cause this condition as well. Best of luck.