How much would the charging slot stuff cost to replace on an iPhone 3GS?

This is an old Iphone of my mother's that has been discontracted and I plan to put a straight talk sim card in it and use it, but my nephew messed up the charger area when he rammed the cord into his own iPhone. I was wondering how much might it cost? At the very least it could be used for an iPod Touch, which it is without a sim card.

You can use Straight Talk, it's fine. Put it on there.
You just can't charge it.

To replace the charging port, it is typically around $30-40. I know my business charges around $29.
The part itself is like $3 which you can buy online. It's the installation that is a pain.
Look on Craigslist for a local business near you that can replace this part for you. It's a quick process.