plugs r fouled most likely and compression could be low if your problem is a blown hg. pull the plugs and look for coolant on em. while you have em out, do a compression test. if coolant is present, recommend replacing headgasket and plugs to start with. second part would be once hg and plugs are replaced, why did it overheat? recommend new thermostat for the "just because" factor while you're doing the hg if the hg is even a true problem with your car.
if plugs are black they are most likely fuel fouled, try known good mass air flow sensor and replace plugs. that's where i'd start if it were me. very common nissan problem.
i'd probably start with the latter. i don't know your mechanical background but the way i read you describing your symptoms....i don't think you could replace your own headgasket....no offense at all. i for instance can't extract wisdom teeth professionally, therefore i won't. i could be totally wrong. but trying out a buddy's maf and swapping plugs is a shit ton easier, and you shouldn't have any problem doing it. ya feel me
good luck,
Dave