The job can be done without removing the head. You will need to have a way of putting air pressure to the cylinder at TDC to keep the valves closed.
Remove the rocker assembly as it will be in the way.
Get the keepers and locks loosened by taping on them with a hammer (brass preferred). There is a cool tool that you can compress the valve-spring while the head is still on the engine( I may be able to bring it up that way in a week or so).
Compress the valve-spring and remove the keepers. then let the pressure off the valve-spring and remove it from the head. Remove what is left of the old seal and install the new seal(there is a little plastic cap that slips onto the valve-stem to protect the seal from getting cut). Install the valve-spring and keepers and go on to the next one.
It is a lot easier to do the job with the head off and it will also give you an opportunity to inspect the valves and top end of the cylinders & pistons.
You may want to replace the valve-guides at that time too as well as have hardened seats installed.

There is enough good in the worst of us and enough bad in the best of us that it does not behoove any of us to criticize the rest of us.
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Be yourself. If you are ever lost, It will be much easier to find yourself if you know who you are!