UPnP is fine to keep on. When it's used on the router level, it's used by clients to dynamically poke holes in the firewall, hence the reason it's required for XBL/PSN to work. Note that it only allows devices on the inside to do that, it won't let an attacker open a hole in your firewall.
Edit: Whew, organizing MP3s is tedious work. I managed to get through 10GB of my collection doing The Works(TM) -- sanitizing tags, standardizing filenames, making genres consistent, removing pointless comments (I literally had a bunch of tracks that had comments like "Track 1," "Track 2," etc), standardizing track numbers and disc numbers, dumping multidisc albums into a single folder, and adding cover art. Even with
Mp3tag it's taking a while, I can't even imagine life without that awesome utility.
Album art is a pain in the ass. The problem isn't finding it, the problem is finding stuff that doesn't look like mushy, compressed garbage. I don't really need high resolution art for use on my PC. I use Rhapsody to play both my local and on-demand streamed music (It's not too bad. At least it's better than my last experiences with WinAmp...it's definitely no foobar, though), and its block for album art is fairly small. Nonono, the issue are my portable devices, of all things. My iPhone isn't too hard to please. Its screen resolution is only 320x480, so a 320x320 image is enough to make everything look as good as it can. But that's not good enough for the new iTouch! Oh no no, that screen's resolution is quadruple that of the older iPlayers. Head over to discogs.com or, hell, Google Image Search and try to find album art that's at least 640x640. Good freaking luck. On average, the best sizes that I've been able to find have been between 400x400-600x600. I was only able to find a couple of them that met or exceeded the demands of the Retina display. The more obscure stuff didn't even come close (I have more 350x350s than I'd like to have).
Ugh. I'm too much of a perfectionist when it comes to this shit.