the valve stem seals will need the head removed as the springs for the valves sit on top of the seals
i dont think you have to remove the valve but just the spring to get to the seals
then the new ones can be oil'd and slipped over the valve stem in to place and reinstall the springs a collets
im sure vocky will have some pics in his build log that show the valve stem seals 🙂
edit;- forund one on google images form a user of this site

edit:- and one more

27-26-25 need to be removed to get to the stem seals #24