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Pete
Yes all Newtonian scopes (a Dobsonian is a type of Newtonian) will invert and reverse the image. You get used to it very quickly.
While it is possible to setup a device that will correct this, it is very rarely done as you lose light every time you use a lens or mirror, and in the end does it really matter? There is no up or down in space!
Also with the size of the moon. Magnification is a function of the focal length of the scope and the focal length of the eyepiece. From memory these little scopes are f4 so they have a focal length of 76x4 or 304mm so your 20mm EP gives a power of 304/20 or 15x. So to make the moon image larger, you need an eyepiece with a shorter focal length, or a bigger scope!!
If you are looking at a 6" or 8", I would go the 8", not that much bigger but much more light gathering.
Malcolm
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