I replaced mine, because they where cheap and I figure, why not do it since I had the thing torn down. However they are surprisingly difficult to remove .

 

you have to get the right tool! My friend had this cool little tool and we got the valve seals off my head really quickly! I changed my valve seals as well when i had my head off for the new headgasket. Cleaned the valves and lapped them etc...

 

Yea I saw the tool in the manual but my auto parts store didint have one. So I pulled them off using some visegrips. I put them on using a socket and tapped them down till they seated properly.