out of your options, go ca18det. obviously get a job again first, save your cash and then do it. in the meantime just get drunk.
gearbox wise, i guess use the ca20 one if it fits (cant remember if it does) until it breaks, they're supposed to be fairly strong as they're the same box as on the maxima, but i doubt it.
once the gearbox shits itself, replace it with one from a ca18de nissan exa.