98 s13 blacktop o2 sensor questions

[Deadrodent]

hey everyone, i'm pretty sure my o2 sensor is bad as i'm showing all the symptoms. I have sluggish revs, smells like gas, gas is coming out the exhaust, and car funs fine on startup but horrible once warmed up..

i have a multimeter and am going to check it out..what are the values i should be looking for?

Can I use a universal/different nissan o2 sensor? or does it have to be s13 blacktop specific?

i'm looking to get this done as soon as possible as my car is running like crap and getting an average 180 miles on 14 gallon tank fills.

thanks in advance!