Think of the telescope as a giant lens that you attach your camera to, so no you don't need an extra lens
just telescope → camera. (they call this type of imaging 'prime focus')
Or, like you said, you can hold the camera (with lens attached) up to the eyepiece and take happy snaps of the moon ect.
(known as eyepiece projection)
I have never done imaging with a dob before so can help huge amounts but I'm sure lots of people will chime in.
by the way, Welcome to IIS
you have surely come to the right place.
Jo