geordie terzo

after a service and check mechanic told me there was play on the driveshaft(nearside)not getting any whinning or knocking but there is a metallic hissing noise (syncromesh?) if you move gearstick in neutral while freewheeling.this noise also happens if you push or pull gearstick slightly while in gear.would it be easier replacing the box rather than replacing parts.thanks for any help