What you likely experienced was a failed set of lower intake manifold gaskets. Possibly the UIM as well, but that is less common. ALL GM 3800's from 97 to mid 05 have issues w/ the stock plastic LIM gaskets, which results in low coolant and can get coolant into the oil. HG are extremely rare. Sounds like you got took on that one, sorry.
BTW, the stock coils are the best things for these cars, so if you start getting misfire issues then I'd ditch the MSD coils and wires and go with an OEM set on both. Then just stick some good Autolite or Delco plugs (NOT PLATINUM) in it and call it a day.
A wooshing noise is an indication that the cooling system needs to be bleed properly. Assuming you are not loosing coolant.
