My advice is to work Ace and put the emphasis on all related aspects of flying in Africa (Tropical weather, hazards related, airmanship facing these hazards, ...).
You'll have both a technical multi choice quizz (Ace will help) and tech questions during the interview. You will be asked to explain the answer to the HR personnel (as Cayenne said); It's not that simple and you'll have to choose your words carefuly in order that he understands.
The interview is quite pleasant and they will assess whether you'll be able to remain more than one month in Nigeria (one year would be a must). If you show that you know how your life in Nigeria is going to be and that you're prepared for that you'll make it.
For the sim, it's basic flying skills in raw data, radar vectoring, steep turn, holding, ILS, go around and another ILS.
Hope it helps
Wish you good luck