I have removed the lower unit and drained the oil, but was having some difficulty removing a few of the screw, so I was thinking about not opening it. Tell me what you think. The oil from the lower unit reminded me of the look of chocolate milk: not clear, not overly thick or thin, brown in color. I rubbed the oil between my fingers and it was slippery with no grittiness. I looked at the bottom of the container and found no metal fragments or shavings. There is no sparkle in the oil indicating metal filings. The spindle at the lower end of the drive shaft is in very good condition: no rounded edges, no chips. The drive shaft turns smoothly in the gear box.
Would these things be a pretty good indication that the internal workings of the lower unit are probably in good shape? Should I continue to work on getting those sticky screw out, or fill it with oil and hope for the best?