Both of the telecommunication companies in the UAE, Du and Etisalat, are government owned, so they block VOIP programs basically to force people to pay them long distance rates. Enter VPN's which almost any Skyping expat uses. It also magically unblocks many blocked websites. There are free ones, but some people have problems with them. I pay $100 a year for vpnaccounts.com and it always works fine.
As far as money, atms are everywhere and most places you can pay with a credit/debit card, although your bank at home may charge a fee for each transaction. Instead of changing money, your best bet is to take some cash from the ATM. The dirham is pegged to the us dollar at 3.67 to 1. 400aed is a little more than 100 bucks.