Before replacing my seals, I was concerned about the guides and whether they might be shot. In the end, it came down to "prevailing wisdom". Not many folks reported having guide wear, but seals seemed very prone. You are correct though, that checking either the seal or guide really requires taking the head off. This was one of the least favorable parts of the overall repair - there was little beyond actually replacing the seals that could be easily done in-situ to prove they needed replacement.

As far as dropping a valve, there are simple ways to avoid this. Its not inevitable!

Paul