No problem, thats why we come here right?
I think I would pull the wheels and have a look. Is the sound coming from the front? It's not very common but I have seen the lining on the brake pad break loose and even fall out.
Gota agree with David , Sounds More like a Brake Problem Knowing that .
As far as Replacing the Booster with the Master Cylinder No it makes No Difference unless The MC is Leaking into the booster , Just a matter of time before it will go out IMO .
I Dont Know why but these days You can Buy it as a Unit a lot Cheaper then You can Seperatlly & I dont like doing things Twice.