The BlackBerry 7230 documentation is on the Blackberry.com website here: Livelink - Redirection
You can also browse through Main Page - BlackBerryFAQ
for some good information on getting started.
Make sure you add a BlackBerry Data Plan to whatever line of service this 7230 will be used on.
Also, since the device was purchased on eBay, it's likely used. It could potentially be hobbled by a corporate IT Policy which you may need to remove.
There's instructions on Main Page - BlackBerryFAQ
for IT Policy removal should you need to do it.