Hi,
If entering as crew Tanzania is fine on a Gen dec and license, but wearing 4 gold bars does wonders for speeding things up, as for visas in advance, they have said it for years as an official line, but virtually all of our guests come in and get the visa on arrival at Dar es Salaam or Kilimanjaro, just be prepared for a que! I am not sure if you can get the visa issued at some other airport of entry here, but I think Mwanza and Mbeya are both ok, they certainly were last year.
As someone said General declarations and lots of dollars, bring a good stack of smaller denomination notes as change is often a problem, also make sure they are all later than 2001 as many countries will not take earlier notes.
Crash