Take it back and make the dealer fix whatever is wrong. There is no way what you are describing is acceptable. Did you test drive this particular unit or another? How far/long was the test drive? What is the wheel base to over all length ratio? Most folks look for a rig that is at least 52% to 55%, the higher the better.
Along with the alignment check your tires to make sure they are properly inflated for the load they bear. This is not your problem, the dealer and Winnebago need to step up and get you into a safe unit. :E