What is the noise level as read on my oscilloscope?
There is a trick to estimate noise amplitude of your display if you have a two-channel oscilloscope. First, turn off any triggering mechanism.
Apply the same noise signal to both channels so that you see something like this:
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Now slide one trace closer to the other. As they approach, the dark space between the two traces gets brighter, but you still see two "peaks" of brightness (one above, and one below). Sliding closer still, the dark space between the two traces increases in brightness. At some point, brightness between the two traces seems constant (please excuse the crude editing):

Now remove the noise from both channels and measure the offset of two channels. This is a crude estimate of RMS noise. It is probably a better estimate than "eyeballing" one trace.
Since the noise you see has a "brightness" that corresponds to a gaussian distribution, the brightness of one trace has a profile like this:

cumulative noise distribution related to RMS