oxygen sensor

need to replace the oxygen sensor on my 94 seville. can't find it. is there a diagram anywhere that shows the location?

if it has a nothstar engine 1 sensor is on tne left front on the exhust pipe
2 is behind the engine between the firewall and the engine on the manifold 3 is underneath after the catconverter.

I think the 93-95 Northstars only had the two. The one after the catalytic converter was used 1996-up due to the OBD-II requirements.