I put in that cheeper alternative off ebay today. Was only $60. They can go cheeper, some go more. Good for the price.
And no, it's not prewired. But I used the directions above and it was great...thanks a ton!
http://myweb.hinet.net/home5/exon/products/automotive/b1/index.html Works fine, compass and temp are accurate. It dims really well and quickly, both in and out. Better than the one I had in a GM car. It dims to like a LCD blue/black.
The thing I don't like it is defaults to the compass deg. and N/S/E/W (as shown in the above link) and not temp.+N/S/E/W. Not a big deal, you just have to push the temp/compass toggle. The big thing I do like is you can turn off the display. I think the Blue is tacky with the orange, haven't seen an aftermarket one that matches yet. I just like the temp once in a while (like before getting out).
It has some UV sensor, don't know if it's worth anything, I'll find out.
Easy install. Took me the afternoon, but I was putting in XM too.
Here is a shady pic (sorry it's dark now):