Yeah the 3G version of the first-gen iPad has GPS. Actually it's very very good GPS -- acquisition time is basically instantaneous. The apps that they sell for automotive GPS are really terrific.

The mounting clip is from a site I found called proclipusa.com. You have to get the bracket that goes on the dash, as well as the one which holds the device. All in, about $80. It's trivial to assemble and mount it -- takes about one minute.

One nice thing about mounting it there is that you can rest your hand on the shift knob while operating it, which makes everything a lot steadier.

There is probably a more modern version of the DiceLink adapter (mine is from 2007), but this one does seem to work fine. It's just sitting there under the passenger seat. You can readily run the cable from the rear CD changer to that location, with no tools.

The only shortcoming is charging. The DiceLink does charge it, but verrrry slowly. To speed it up, what I did was, I simply put, under the seat, one of those pass-through fittings onto the end of the cable that comes out of the DiceLink. The pass-through fitting allows you to plug in a mini USB power cord. You then just connect that to a 2.1 amp charger that you put in the cigar lighter ($10 at Best Buy -- NB it has to be a 2.1 amp one for the iPad -- it needs more juice than a simple iPod) under the glove compartment, and you have plenty of recharging capability. Trivial to then just tuck the power wire out of the way -- you don't even see it. Then you just run a regular iPod dock extension cable from the pass-through fitting up to the iPad. You then have 100% functionality and quick charging. It sounds more complicated than it is.

Lastly, an iPad obviously has a fair bit of glare, but it seems pretty tolerable. I will order one of those anti-glare screens for it from Amazon; maybe that will help.