The buzz is the solenoid in the e-unit (reverse unit). Two things are happening that make it louder than it would otherwise be. The buzz is gets louder as higher voltage is used to run the train. Your train is probably running at higher than normal voltage because it has not been serviced in a long time, and is all stiff and gimpy. New lube and some running in will help with that. The second thing is that, if I am not mistaken, your GW-180 transformer uses pulse width modulation to control the voltage level (search that term on the forum for more information). E-units buzz much louder when run on transformers of this sort. Not much can be done about that, short of switching transformers.
As for the whistle, make certain that no part of the circuit board is touching the metal frame of the tender. Also make sure that none of the leads for the individual components on the board are touching each other (this can happen on these older boards, where the resistors, diodes, etc., are placed vertically).