All mp3's should be safe. I don't think viruses can be sent in an mp3. It's still a good idea to scan every file before opening them.
*Note that
Fake files are a problem on the network.
I have no idea what the chances of getting caught are. Keep your shares to a reasonable number(It's been posted to stay below 1000). It also depends what country you live in. In some it's perfectly legal to d/load as much as you want, in others it's not.
Try running
PeerGuardian 2 while your using LW. It works like a mini firewall for file sharing programs. It helps keep undesirables from keeping tabs on you file sharing activities. It's not a guarantee but it helps.