Hi Chuck! Welcome to the forums. We have an Argosy Minuet 6.7 metre. Larry has replaced both gray and black tank valves in ours. Are there access holes cut into your belly pan? This would indicate that the valves have been done before. If more than the valves are damaged, then dropping the pan is probably the best way to access them and the plumbing, as well as the black tank. Removal of an entire bath to get at the top would be more work than dropping the pan.
Hope you can get the trailer on the road and camp with the Ohio Airstreamers. We usually post on this thread: http://www.airforums.com/forums/f290...tml#post690155
This weekend we are at Mohican SP, which isn't too far from you. You are welcome to camp or visit. We will be arriving there on Fri. afternoon.
Hope to see you down the road. You can PM Larry if you have any questions.
Lou and Larry