I finally got my hands on a CO2 tank yesterday and it is filled but not the cleanest (quite dusty). Is this somethign I need to worry about regarding sanitation (ie do I need to clean/sanitise the valves)?
I would give it a decent wipe down to get rid of surface gunk. Other than that, not much is going to survive in a pure CO2 environment so I wouldn't worry about sanitizing all the valves and everything. I don't sanitize the gas lines going into my keg. Just make sure it's not going to blow the surface dirt/dust into your beer.