how can I reschedule my interview because the date they give me was the date of my work day..

From my experience, you can go for your interview anytime after your interview date has lapsed. My wife was able to get interviewed and processed by just showing up with me a month after her interview date. They just will not attend to you BEFORE your interview date. Good luck

What do I need to travel to Nigeria. I have American passport. Do I need to do a visa just visiting fior 2 to 3 weeks

I second what Kobi said.