[georgeckc]

I m using Alltel. So I am not 100% sure about your charges would be.
However, from what I read from here, since all those softwares using ICS, Sprint would not be able to detect you "cheated" on it. There is people report no changes on their bills after using those softwares.
But Sprint going to put cap (if they haven't already done so) on usage to 5gb per month (not so unlimited)

As for which softwares, if you just need it simple and doesn't need something like port forward or connect your device using bluetooth or USB. You should try either Wifirouter or WMWiFi. I never use WMWiFi before, but WifiRouter is pretty easy to use and setup. The latest version is not free. However, version 0.91 or older is free and you can find it here with detail instructions. I am using 0.91 version and is working pretty good for me.

Since those softwares using WIFI of your phone, it will drain your battery pretty fast and deliver quite a lot of heat of the phone which could damage the phone. A piece of advice, plug in the phone to charger while using the softwares and slide the keyboard out, take off the battery cover to let air flow better to reduce hear. If possible, put a small fan behind the phone would be the best.

Hope that help you.