To obtain those four signatures, expect a waiting period of 2-3 months. The person to see is Mr. Amadi, Chief, Radio Communications Section. Best time to reach Mr. Amadi in his office is between 0800-0830 hrs. In a later stage, copies of your national licence and your national passport are required. The licence is valid for a period of one year.
Renewal fee is less.
To obtain these signatures only, generally takes 3-4 weeks. That should cover whatever you want to do. There exist extremely high taxes on import. Customs Officials will search luggage upon arrival. Make sure you have watertight documentation.