I'm no mechanical genius and this is all i used:
- jack up
- wheel off
- undo two strut base bolts and push off to side, keeping lower control arm supported by a upside bucket (that's what i used)
- maybe undo brake line support things (a bolt each, nothing major)
- undo top three bolts
- drop it all down and do ya spring change i guess
Take off the wheel and have a look, it is really hard to mess up. Make sure you get a wheel alignment after you're done because everything will be out of whack.
there's a link to the altima workshop manual somewhere here, have a search.