Yea, as above, GPRS is just a technology for accessing the interet from your phone. It's a pre-3G technology, and slower than EDGE too.
Ringtones may or may not cost you money. If you buy from one of the companies that show the annoying adverts on TV, it'll probably cost you a few pounds, an often puts you down as a subscriber so you keep paying.
A free alternative is to use a program like Audacity to edit an mp3 file on your computer, cutting down your favourite song to just a ringtone chunk, then using Bluetooth or USB cable (whatever your phone supports) to send it to your mobile, where you can then choose it.