Nigerian here.
I can confirm that SmartLynx does in fact have a contract with Air Peace. I've seen the planes several times on FR24 as well as physically. As for the experience of living in Nigeria, I assure you that it is different from many other places.
Air Peace is based in Lagos, which to be frank is a very challenging city to live in with crazy traffic jams and rascals around (if you wander to certain areas). I expect that you'll be staying in a hotel or something and have some form of living services offered - company-provided transport arrangements, etc. It's not the best place to stay, but some foreigners make it work (there are many expats in Lagos).
As for the routes, I've seen the A320s used on routes to Lagos, Abuja, Asaba, Port Harcourt and Kano. I think those are the only airports they are operated to.
If you do happen to take the offer and end up in Nigeria, I'd be happy to link up and give a few tips. You can also shoot me a pm for questions.