Oslo airport is about an hour of driving north of the city center. From there it is about 45 minutes of driving from Oslo to Drammen. I would recomend you fly with Ryanair to Sandefjord (might be called Oslo , Sandefjord at the flight booking). Sandefjord is south of Drammen & abit closer. Hotel rooms etc. in Drammen is not a problem , expect to pay around 1000 NOK per day at most hotels.