Head Has To Come Off - Any Sage Advice?

My Trophy 900 is being very naughty, I know some of you will have read my previous posts about it sounding like a machine gun. I have concluded that somebody with limited ability has been in there previously and bent a valve slightly so that it does not return properly. They have mixed up all the cam retainer caps and there is silicon sealer everywhere. There is also what looks like some sort of graphite based additive in there that has been put in in an attempt to quieten things down. Didn't work. So now I have to get the head off, Haynes says it can be done with the engine in situ but that the liners have to be resealed. anybody got any advice or pearls of wisdom that could save me from losing what's left of my sanity? I'm a pretty decent mechanic, I work on outboard engines for a living but I've never delved this deep in to a Triumph motor before. Thanks in advance. Dave.