XD100 in the tank looks blue green, but I don't know if there's any way to tell what's actually in there, other than siphoning it out, and refilling it. If the label is there, it probably IS programmed for XD100. Only a dealer can change the oil setting from XD100 to XD50. I would think that any dealer that changed it from 100 to 50 would have taken the tag off. Again, you need a dealer to verify the setting.
I'm not sure about the lower unit oil, but I would assume it should be pretty standard. For answers from the ETEC gurus, ask here: http://bbcboards.zeroforum.com/zeroforum?id=51
Best ETEC info I've found, including several very experienced and knowledgeable technicians.
Oil alarm I think I've heard about on the BBC board, but can't remember the answer.