I had a Nissan pick-up with an LSD. The two major disadvantages for me was: 1) When I got in a really tight spot offroad, the LSD still slipped, with one wheel spinning. 2) On icy highway roads, you are much better off with an open diff (with selectable locker) vs. an LSD, because both wheels will lose traction, and you'll spin out much easier.

I have always been of the opinion that if you are on snow or snow ice conditions your traction can benefit from lsd or locker but with either it is up to the driver to be careful since applying the brakes is just as likely a cause of a spinout as too much gas. On the other hand if you are on a large patch of ice and just ice your pretty screwed anyway without studs or chains <img src="/forums/images/graemlins/zombie.gif" alt="" /> just hope you are on a level surface or not going into a turn <img src="/forums/images/graemlins/scared.gif" alt="" />
Curt

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.