Welcome aboard.
You might want to start with this read here:
zerothread/178710
I thought this problem would have been fixed by now, but it hasn't been and my spec is a 2002. I'm having an oil consumption test being conducted now and it seems to have stopped burning oil. Went from using 10w-30 mobil 1 to the penzoil the dealer put in for the test. I'm a bit confused about the situation, but I have also learned the Suby owners were having some problems with the mobil 1 as well. Pre-Cat failure is your worst enemy and most say put a header on so the problem doesn't occur. So yes, I said mod your car so it doesn't blow up down the road. The motor does respond well to mods though. I/H/E and you will be happy with the performance of the car. It also handles quite well, even on stock suspension. Did you get brembos? Post up some pics and there is a sentra owners thread floating around. Introduce yourself in there and post up the some pics. in there as well.
Two recent threads on the precat problems:
zerothread/188626
zerothread/186031