Help with diagnosis
 

My 02 3.8 with 95K started missing yesterday. Trouble code says the O2 sensor in bank 1 is gone. I went ahead and got spark plugs and changed those and wires, as the ones in looked like OE. Checked my oil, and it has something in it. Not coolant, as I'm running water only right now due to a coolant leak. Anyway, whatever else is in the oils looks very frothy. It looks thick, but it's not, and seems a dark yellow in color.

Oil level isn't rising, so if something else has appeared in the oil, not much has gotten in. I'm thinking the two problems are unrelated. So my question is: what in the world is happening to my oil?