Valve condition: There's visible evidence of a good healthy "margin" (edge of the face) protruding slightly above the chamber head in most of the chambers and valves. The valves don't have excessively crusty deposits of uneven burn patterns.
Oil seals: Many of the chambers show light oil staining that has wept past the valve seat. This isn particularly noticeable on the intake valves, being larger.
Combustion efficiency: The evenness of colour was what I looked for and #5 showed somewhat sootier in an even fashion. That implies to me, the oil is being fairly evenly misted into the chamber from blow-by, rather than sneaking in with the fuel/air. #1 is rather whiter in the chamber, and the piston top clean; this suggests hotter combustion temperatures.
New guides will usually be part of the new valves unless the old ones are a tolerable fit. The guide is used to centre the seat cutting tools, so this is why it matters. The oil seals are replaced as a matter of course, unless you are specifying the cut-in teflon type. Many motors delete the exhaust oil seals and some don't even worry about the intakes. It depends a little on head design, too for how much effect the seals have.
Hope this cleared up a few questions!
Regards, Adam.
