Nick
1) take the engine apart and put the power wash to her. Use gunk or similar brand engine degreaser or even can use oven cleaner. It would be a good idea to remove all block oil galley plugs. No, it will not hurt cam bearings ( or shouldn’t). I would inspect everything nonetheless before reassembly. A compressor to dry off the block and if you have a rifle cleaning brush, run it through the oil galleys. All cavities should be blown out after being washed. And you really don’t need a high pressure sprayer. Regardless of garden hose or h p spray, if you are not soaked and as wet as the block when through, you were not thorough enough.
2) as long as bearing surfaces are not damaged, reuse. Don’t worry about discoloration. Some brakecleen or carb cleaner could be tried to se if it takes off the stains, by all means do not sand or use any abrasive or lint from rags. Best to blow them dry and set out to reinstall. I am a little particular in that I keep everything, bearings-bolts-nuts- rockers in order and put everything back in it’s same place. So each bearing goes back from where it came.
3) I have no idea what shins you are referring to, but newer technology gasket materials are superior, so I would use new gaskets.