yeah if it was the engine not getting enuff air, then it would seem like a weak car, but the response to the wheel should be fine ( quick take up ) but just weak if it were injector / intake problems...
just to check the engine, put it in neutral and give it a nice rev to see if its ok...
since it seems its your g/b, i'm sorry , you'll have to take it to a mechanic to have it sorted....
good news is it shouldnt take long at all the check out the clutch, it can be removed as a unit fairly easily / quickly.... i think its the pressure plate myself, clutchs tend to go on cars that have done say 140-150 tho kays, so thats like 100k miles + or 10 yo and beyond depends on how its driven....
if it is the TC, that could get costly since its harder to take out, i banking on the clutch which would be a good senario , they only cost like $500-600 Aud (inc labor) thats only like $250-300 USD ...
please keep me posted, and i hope i helped in anyway....
btw, if your mech says he can replace the pressure plate, refuse it, get the clutch replaced as a NEW unit and make sure its an OEM unit (daikin i believe make em for nissan altimas)
cheers
joe