We have the same trailer, but I have the dealership do all the winterizing and dewinterizing. That way, if something goes wrong, hey, it's not my fault! ;-hap
As for the knocking water pump, what faucet did you have open? We have a Sur-Flo pump in ours and it has 2 different "flow modes" I guess you could say. When a faucet is not wide open it goes into low flow mode and it sounds like a machine gun, i.e. tap-tap-tap-tap-tap-tap, etc. And it is louder than when it's in high flow mode when a faucet is wide open, which then the pump runs normal I guess.