Just set aside three or four hours this Saturday, (preferably inside a nice warm garage if you are lucky enough to have access to one) and take your CAI
off and inspect it; see if there is any water in the bend, check the MAF for water damage or corrosion, etc.
Then take a goose neck flash light and look inside the throttle body; if there is visible water in the Intake
manifold then your f**ked, and unless you know how to fix it yourself then it will cost you lots of money to have someone else fix it.
If however you see no signs of water, and the engine is running okay; then do what your mechanic said change the oil and consider yourself lucky.
You still have never said what the deal is with your CAI
filter; is it exposed to the open road because you don't have engine or wheel well plastics in place?
If you do have the plastics; are your wheel well vent holes covered up? Got a heat shield or splash guard? Something?
Because if the answer to all those questions is no; then you need to do something to stop wheel wash, and splashes from things like hydroplaning and what not, from so easily getting on and in your filter. Think of it like a sticking a shop vac hose under a lawn sprinkler.