Hey, I'll take a stab at it, B1S1 or bank 1 sensor 1 is before the cat, the first on in the exhaust. The sensor you're looking at on Ebay is the universal kind, you'll have to wire it into your plug. As far as it bein stuck, they usually come out without too much trouble. Just get a socket or box end wrench on it and pull like hell. The threads are sealed a little bit from the outside, so they usually will crack loose, but the threads on the inside are sometimes crudded up and can screw up the threads up comin out, so go slow. If it won't crack loose you can use heat, but that will sometimes screw up the threads too.
Hope this helps! Matt