Since I quit smoking, I feel dazed and unable to concentrate. Is this normal?

Yes. One of the reasons people smoke tobacco is that it gives them greater focus and attention span. Nicotine withdrawal often produces the opposite - impaired concentration and focus. It will pass. If it is severe and causing your problems in everyday life, the use of nicotine replacement (patches etc.) with gradually decreasing doses will help. Talk to your health care provider.
Depends. Nicotine withdrawal starts within 12 hours, peaks in 48 hours andseems to take up to a few weeeks to resolve. These symptoms are normal when in this time frame.