There's no need to credit everything no. In Masques, I credited the makers of the brand of tazer I used simply because I lifted the text of the ad from its website almost verbatum for use in the story.
And if you were having your characters quote huge tracts of some RL Professor's scientific research, say - or, as you point out paraphrasing the text - you could always add a list of sources at the end of the story.
But other than that and in the circumstances you cite, Jen, just looking up the facts of everyday bits and pieces - no, you wouldn't have to worry about it.
LabRat
