Emission Systems And Parts

I got a 91 Plymouth Laser 2.0L Non turbo and the engine is running real rich i removed the o2 sensor and its pretty black, blacker than usual. but i got a 03 dodge caravan that failed the etest and i bought a new o2 sensor for it but it turned out to be the egr valve that was at fault. i was woundering if the 2 o2 sensors would be the same? i matched them up theres no real big difference the threads are the same and it threads into my exaust manafold i would have to change the plug but thats no big deal but would the o2 sensor work?
i was on partsamerica.com and i found a universal one that looks identical to it so i hooked up the wires and tryed it and it seems to be workin but how would i know?