Hi and thank you for your email.
Not quite sure what you mean by a plugin. We do not read CAN bus signals, our oscilloscopes just look at analogue signals. So you can certainly capture the waveform, however you will not be able to translate that using our software. If you were to write your own software and you enough about the CAN bus signal then you may be able to do more.
In terms of voltage a +/-5 Should be fine, if you are unsure about the voltage you can always have in on auto range and then adjust once you a see a signal.
Hope this helps.