I read an article that gave me the impression that using a camera's high ISO noise reduction doesn't help when using raw files and Lightroom, as the raw file does not contain the resulting noise reduction. Any truth to this?
Yep, completely true (noting of course, Bart's caveat above - I think the Pentax K-5 for example, has Raw-level NR applied to higher ISO files). Generally speaking in-camera NR isn't "baked in" to the Raw, but is simply a metadata tag that lets the camera company's proprietary conversion software know how the camera was set, at which point it will apply that same setting from within the converter.
An exception to this is long exposure NR - that is
embedded in the Raw, being generally an in-camera dark frame subtraction.