mis behaving gearbox

[scarab green]

please can someone help:argh:, im having grinding and jumping issues with the 2nd gear, then when in 2nd with the clutch out as the car is slowing down you can hear this whining noise(funny sounding)
is this perhaps a synchro problem if so ,whats the cause as well as whats needs to be replaced and the costs envolved, thanks guys
this is a bmw e46 325i