Most of the torrents are good quality. There are very few fakes because a few people will find out that its fake and won't download or seed it. That means nobody else can download it and the torrent dies.

It is very hard to tell a difference in quality between 160kbps MP3s and the actual cds. Oh and the better the quality is, the more space each file is going to take.

If you've never used bittorrent before, google it and read up about it. Its basically goes like this:
1. Someone wants to share something so they create a .torrent file. This contains the list of files, the file sizes, and other info about the files included.
2. You either save the torrent or open it directly into your bittorrent client and it downloads the files.

Anyways, I use uTorrent (www.utorrent.com) because it isn't as resource intensive as some clients. www.torrents.to is my favorite torrent search site.

EDIT: If you want to keep all the crap off of your computer, I would suggest Spybot Search & Destroy. Its free and its recommended by all the computer magazines for a reason.