Since most lunar exposures will be very short, an off axis guider is not needed here. Off axis guiders are more useful when taking long exposure prime focus shots of stars and faint nebulae as it allows you to choose one of the stars near your subject in order to guide the scope. In short, the whole scope acts as a huge telephoto lens. I was quite pleased with the results as this was my first attempt at prime focus photography. The full moon is probably a good subject to photograph for your first prime focus shots as the moon is so bright you only need short exposures.
Short exposures mean sharper images with less chance of trailing taking place.
Prime focus lunar photography can be done through most any scope provided it has a rigid, clock driven mount. Polar alignment can be less precise related to the fraction of a second exposures. Be warned, if any drift occurs related to overly sloppy alignment, this will result in blurred or less than sharp images. Another consideration is balance as mounting a camera on the back of a SCT or on front of a reflector can result in the scope being back or front heavy. Several good books give details and exposure times for prime focus astrophotography.