Going in from Guthega is the cheep but physically harder option. You just have to pay for park entry (& chain hire if you don't have them). Going in from Charlotte Pass is easier but EXPENSIVE. Last winter the costs were $56 for the Skitube (both up & down), then $35 each way for the snowcat between Perisher & Charlottes. Thats $126 per person - although after about 1 hour on the trip in from Guthega, you'd be happy to pay twice that.
It takes about 2hrs in from Charlottes. The best I've done from Guthega is 4.5hrs with skis in fresh snow, although it usually takes much longer.
You definately need either snow shoes or skis - depending on your skiing ability with a heavy pack on.
Also, don't camp in the catchment for Blue Lake and/or Hedly Tarn!