Vilanculos is served by an international airport...
The bus system (chiapas) carries passengers both South and North, running every day. However the roads are not always in the best conditions so be aware of this when planning your journey. The journey time from Maputo to Vilanculos is approximately 10/12 hours.
Little bit more expensive, but much faster and much more comfortable:
One month visas are issued at the border or airport. Alternatively they can be organised before entering the country at any Mozambique Embassy (South African passholders no longer require an entry visa).