1997 Blazer S.E.S. light on AGAIN!

[HOSSMAD]

1st time to dealer,SUV died on road, replaced fuel pump,and sending unit,about $800.00 got on road 6 hrs. later car died, different dealer replaced ignition switch, (which it had been acting up),and coil wire.At that time, It turned over but wouldn't start, sometimes dash lights lit up sometimes not.Next day, S.E.S. light again,this time, replaced (Plastic)???????, INTAKE gasket that goes bad on ALL these models,and replaced the water pump (leaking) and an axle boot losing grease.Another $700.00.Get on the road about 2 days /50 miles, S.E.S. light on AGAIN, Now too cool air coming from cat. converter. loses power on highway , scared to drive it out of neighborhood where it runs fine.I could just replace sensor behind it $116.80, before replacing the converter itself, but , am i to expect another code afterward?Anyone have any experience with this sensor, does it go bad usually?, or the converter go bad first?