Oxygen Sensor

I was in the DeVille the other day, and I decided to pull up some codes. So far I got E13. Thats something about the right oxygen sensor not ready. Is that something to be alarmed about or do I just need a new oxygen sensor? I heard on this car (92 DeVille) there are two. If that's all I need, then I'm gonna replace both of them. Someone let me know...please

BTW, what is F47?