Air intake Sounds? and engine cleaning?

Two questions.. I have a cold air intake on its way.. Ive read the prior intake questions on what brands and how to install.. But my question is after installed, what do i listen for? Rattles?? Air Leakage? Too loud, not loud enough? And the other question is when i pop the hood....MAN ITS DIRTY! I'd like to clean it up a little before i install the air intake.. How should i go about cleaning it up? im sure just taking the hose to cant be to good for it.. Should i wipe it all down by hand?(98 blazer by the way. not like it matters)Thanks fellaz