afroken

I've heard different things....car makes a clicking noise when in neutral, if i depress the clutch noise goes away. if i let off the gas in 1st or 2nd it whines REALLY loud unless i press the clutch in. the noise is also proportional to rpm. i've heard throwout bearing, or even worse input shaft bearing. my question is what do you guys think and also could someone explain how the input shaft works? does it spin all the time? could it be diagnosed by testing for lateral movement of the shaft? and also your experiences with the problem if you've ever had it.
thanks
phil