you will probably want to read articles here…
specifically:
http://www.nissanperformancemag.com/projects/perfspecv.php
and:
http://www.nissanperformancemag.com/projects/racespecv.php
other than that you should have bought a 2000 Sentra SE with a SR20DE RR in it. Biggest tip is to put locktite on those butterfly valves and check the oil every 500 miles. Then mod away.
not everyone buys built and sorted cars like you.