i recently installed an air fuel ratio gauge, and now my cel is coming on, and its my o2 sensor....i checked all the connections and it was installed properly....could it just be "perfect timing" that when i installed my gauge the o2 sensor just happened to go, or is it something more serious

Not sure bout your problem, but an air/fuel gauge isn't gonna work with a stock o2 sensor. You gotta put a wideband in.