400E/119 Valve Seal Replacement

[emerydc8]

My car needs valves seals and I was thinking of doing it myself. While the valve covers are off, I was thinking about replacing the upper chain guides and tensioner. I've never had a timing chain off an overhead cam engine and, with 32 valves, I'm not sure I want to risk not getting things back together correctly. Can the seals, guides and tensioner be replaced without actually removing the timing chain? Also, how hard is it to replace the valve seals? Is there a risk of dropping a valve into the cylinder on a job like this? Any special tools required? Thanks.