Hi , Idireland.
We also are new owners of a 2003 Classic 30.
After we purchased ours we found out the rod that connects to the black tank valve was broken at the valve. There is nothing binding on the rods themselves, the problem is the valves. You can try to find something to put into the tanks to lubricate the valves, but if that doesn't work, the only thing left is have Airstream replace both valves. It's expensive, I know, but you will end up with brand new valves.
If you go the Airstream rout, also have them replace the fresh water tank drain. It will break sooner rather than later and you will not be able to replace it your self ( ask me how I know).
Also have them replace the bathroom fan with a Fantastic fan. Life is so much better with that upgrade.
And while your at it, upgrade the toilet. A new porcelain toilet is the way to go.