The Zambian Currency is the Kwacha, not to be confused with the Malawian Kwacha.
The rate is around 3,700 to the USD$.
There are VISA ATMs in most reasonable sized towns, try Barclays or Standard Chartered in town close to the post office.There is also a Barclays ATM at the Sun Hotel complex and a Standard Chartered ATM at the new Falls Park Shopping complex in Livingstone. Only VISA cards or cards carrying the VISA symbol can be used in the ATMs. Mastercard and Cirrus Maestro cannot be used. Both VISA and Mastercard are acceptable forms of payment for most activities and accommodation, though CC use attracts a surcharge of around 5%.
Try and avoid using moneychangers on the street as they will likely try and rip you off by, for example, confusing 500 Kw notes with 5000 Kw notes.