Here's a pretty good comparison between options: http://www.tacomaterritory.com/forum/showthread.php?t=1328&highlight=limited+slip

To try to answer your questions:
1. The TRD LSD's are heavy-duty and really long lived, really depends how how hard you beat on it.
2. Install is easy, just be careful remving your carrier bearings.
3. Nope.

You can get it from www.trdparts4u.com for $199 shipped.

The best Toyota parts deals are here:
www.trdparts4u.com
info@trdparts4u.com