is it possible to connect to the internet via wi-fi without paying for the monthly internet plan?
i have an 8320 from t-mobile by the way.

Yes it is very much possible.

how do i go about doing so???

Connect to your WiFi network... or some WiFi network that you have access to.
Open up the Hotspot Browser, and start browsing.

Do you know if T-Mobile will charge for this service even though you're on your own wifi network at home?

And is there anything that you can't use such as the google maps or jivetalk and email applications unless you have an internet account with T-Mobile?

No, you won't be charged for the use of your own WiFi network.

I have no idea which apps you can use via WiFi exclusively.
There's a FAQ article at blackberryfaq.com which details what you can/can't do without a BlackBerry Data Plan.