We work about 8-10 weeks in Nigeria per year and have been there on a rotational contract as well, based in ABV.
While the country certainly has it's drawbacks, it is by no means the DRC... Abuja is generally a pleasant experience, hotels of acceptable standard, and will agree with exeng - unless you attend local church services or hang out at the UN HQ, the biggest danger is the standard of driving, especially in LOS.
Having the right kind of driver is very important - he is the make or break of the daily life, and if he doesn't show up more or less on time when ordered, not only working but shopping and living in general becomes tiresome.
Armed guards should not be a necessity except in certain outstations, but depending on what clients you are looking at flying it may all be incorporated in the contract anyway, whether you need it or not.
Accommodation is generally in secured compounds with armed guards, keeping break-ins etc almost unheard of. Of course you need to watch where you are going, but most places in ABV you can drive safely at night, and some in LOS too. The crime that does occur - should the worst happen - is either simple or armed robbery, but people are not murderous, so if you throw your wallet in one direction and run in the other I doubt they would even give you a second glance.
The other problem is being '419ed', linked to what exeng said about people having a rather wishful relationship to the concept of truth. Never believe what people say to you if you really depend on it - asking in 5-6 different ways sometimes produces something approximating veracity, especially when things are aviation-related.
Flying intra-Nigeria is easy (when you get used to the radio - give that a week or so), but you have to have loads of patience. The good thing is that your pax will be used to how things work, so an explanation that in EUR region would have resulted in irate disbelief is just greeted with a smile.
Another good thing is that 90% of your pax are scared s...less of flying, so if you say "can't do - wx not good", they will thank you and take whatever alternative you offer them.
Things go slowly, so if you can adjust yourself to the pace and don't get stressed by it, flying in Nigeria is a rewarding experience. Be prepared to occasionally shout when you are being treated like a schmuck and equally prepared to "facilitate" things with 500 or 1000 NGN now and again.
Health insurance can be obtained, although you will pay upwards of 2000 GBP/yr for the pleasure.
Any further q's just PM me - cheers ;-)