If you look on Xterraparts.com I think they have an installation guide. I remember seeing it somewhere - and yes, it involves a fair bit of wiring, since it must also be hooked into the reverse gear (so it automatically un-dims so you can see) along with power, headlight sensor (so it doesn't dim during the day) and the temperature probe.

I happen to like that mirror and wish my X had it. I'm considering getting it aftermarket and doing the install myself, but the costs I've seen were kinda high. I think though, that they can be had for $216 or so.

Also, check out Mito Corp. which has these same mirrors. The installation instructions are there also.