Not only am I a nursing mom (he's 17 months now) who used Medela Pump in Style, I'm a CLC and WIC Peer Counselor. As a mom, I would tell you that your milk never comes close to the tubes, so it's really not an issue.
As a CLC, and from the training I had, it was explained they same way, but some solutions were suggested...
If you just want to get rid of it, drench the inside of the tubes with rubbing alcohol (submerse the tubing) and then do a rodeo-style, over-the-head circle (with a rowdy yee-haw if you wish!!) - that should clean the tubes. It's also a method you can use to dry them.
In the future, try not to get them wet - they don't need to be washed (just wipe down the outside from the static-cling dust!!). If you notice a few drops of water in them - like you said, it probably comes from pumping when the bottles aren't all the way dry - just let the pump run with the tubes attached... the motor will suck them dry!
I have no idea about the warranty - sorry!
Happy pumping - keep up the great work :)