Hello,
I don't know if this answer is too late...
The "main" shopping street in Oslo is Karl Johan, it starts at the Royal House of Norway and ends at Oslo S (Oslo Central Station).
Near Oslo Central Station there are shopping centers close together ( Oslo City, Byporten, Arkaden, Gunerius og Østbanehallen)
There are also a shopping street called Bogstadveien.
You can also visit Aker Brygge for fashion,shopping and food.
Other places worth visiting:
- Oslo Opera House
- Vigelandsparken
About Prices:
Dinner for two can cost you from 36,77 to 49,03 EUR
A Coca Cola 2,7 EUR, and a pack of cigarettes 8,58 EUR
(1 EUR = 8,16 NOK)