Ebay is the cheapest place, yes you can use MP3 ringtones, you will need the motorola mobile phone tools too so if it doesn't come with the cable you will need to buy it seperaetely.
You can do a lot with itm that's a question with a long answer. What do you WANT to do with it?
You can copy photos backwards and forwards though the mobile phone tools too, games are a bit trickier. If you can find Java games to transfer over you'd be able to do it but when I had my V600 (the smae phone essentially) I never found anything I could put on it.