In response to an enquiry:
We signed up with Goecco before we went iceland, need to book ahead because they are pretty popular. In fact most of the tours there run out very fast because iceland is starting to get more and more popular.
The details of our tour is:
http://www.goecco.com/winter_tours/iceland_ice_cave_winter_tour_-_2_day_tour
We went for the 490USD per pax, thinking we will be sharing our room with 4 other people. We ended up having a room to ourself. The room has 2 double decker beds. There will be a shared bathroom but still not so bad.
The cost of living is relatively high in Iceland. You need to pay like $18 for just a bowl of turnip soup and that's normal. So food is relatively more expensive.
For our trip we only went for 4D3N. But I will recommend 7 days due to the fluctuating weather. We are very lucky to have good weather for 2 out of the 4 days we are there. Heard from some friends who went and faced with bad weather. so they didnt see much.
Self-drive is possible, if you are confident about long hours of driving and wet snowy roads. Sometimes when weather is bed, you will see nothing in front of your windscreen. We went during winter and decided not to drive. In summer, it is much better but it will be packed and accomodation will be more expensive.
