which side is bank 1?

97 taurus 3.0. got a PO133 fault, sencer 1 bank 1. Question? Is bank 1, sencer 1 the sencer in the exhust manifold between the engine and the firewall? and are the sencers hard to unscrew?

See this thread where I get totally confused with my explanation,
http://www.automotiveforums.com/vbulletin/showthread.php?t=660385,, bank 1 is the rear between firewall and engine,, I know there is a special socket for o2 sensors, but possibly some can be removed with regular wrenches.. I've never had trouble removing one..

Question? Is bank 1, sencer 1 - On my 03 Vulcan it's near the firewall on top of the exhaust manifold before the cat converter. Rent the special tool at an auto parts store and take you 15 minutes to change it, sensor runs about $40.