What plan to get for an iPhone 4s?

I'm getting rid of my 4th gen iPod and getting an iPhone 4s. I don't know anything about Wi-Fi or internet but i've heard the 100mb plan will mean I have little internet. Once the 100mb runs out, will I still be able to connect to Wi-Fi? Is the amount of 1S00mb the amount of 3g I can use a month?

Yes you are still able to use Wi-Fi internet after your 100 mb runs out. The 100mb IS considered little if you go on the internet alot, but it's enough. All that 100 mb means, is that you can go on the internet when you are NOT connected to Wi-Fi, so when you aren't home. When you are home, it does NOT use up any of your 100 mb cause you have your Wi-Fi. And when your 100 mb DOES run out, you definitely ARE to still able to use Wi-Fi to go on internet.