Switching from Blackberry to iPhone 4s?

So i have a Blackberry Bold and I wanted to buy an iPhone 4s off Kijiji. I'm on Rogers and the iPhone I'm buying is locked to Rogers.
I was wondering what i need to do in order to use the iPhone. For example i know iPhones use micro sim cards. Where and how can i get a new sim and keep the same plan etc etc

Please any answer will help a lot

Why can't I watch videos taken with my iPhone on my computer?

I took some videos today with my iPhone 4s and I tried to watch them on my computer but it doesn't work. When I click on it, it just shows a black screen but I can still hear the sound. I tried to delete my quicktime and download the new version but nothing changed. I've also tried to watch the videos on iTunes but there wasn't any difference. I don't have a Mac by the way.

Is it still safe to use my iphone if a piece of the front is missing?

I broke the screen along witha good chunk of the screen around the camera. I can actually see the camera inside my iphone. Anyway i was wondering if the phone was still safe to use or dangerous because of radiation and chemicals inside the phone. Thanks for answering.

Added (1). @420blazer called the hazmat team and they told me to *** off. Now I feel bad

Which one is better, iPhone 5 or 4s?

I want to change my phone from blackberry to an iPhone. Well, I'm planning to change into an iPhone 5 but since I heard that iPhone 5 has many problems, I might go with iPhone 4s instead. What do you think? IPhone 5 or 4s?

How to sign out of twitter on the iPhone app?

They said delete your acc. From the app, but I don't know how to do that. Or they say delete the app and i did that, but when i installed the app again, I was already signed back into my other twitter

My iPhone Internet won't work without Wi-Fi?

I have the 4s. The Internet doesn't work without Wi-Fi. It always used to but lately the Internet has only been with Wi-Fi. This includes my google app, my YouTube app, and my radio app. And my email!
What should I do? I need it to work without Wi-Fi.