There are both battery and switched ignition tiepoints at the back of the underhood fuse box on the driver's side. You take the 'fuse deck' out and at the back you find 2 or 3 tiepoints in the form of stud-with-nut and oodles of wires connected there.

There is an EASY path from there into the area under the dash, once you get the "fuse deck' out of the box (you can pull it up and away maybe 2 inches), shine a bright light into the area near the studs in the back. NOW, open the driver's door and take the fuse cover off the end of the dash - you will see the light shining in there. Use a stiff (and preferably nonconductive) wire to fish the wire from the box under the hood to the area behind the light switch.

You can then run it down under the carpet to the seat area. YOu'd probably do well to remove the trim around the door opening to route the wire. Many of us have had to open that area up to run new, heavier speaker wires.

Do not try to find power enough for a seat motor under the dash. Sure, you can tap the feed to the ignition switch - but you are setting yourself up for a "Dr. Phil" moment, instead, get your power where they did for the seats and for most of the high current stuff in the car) - that tiepoint in the fuse box! (Now REALLY high current stuff, like hte 50 amp run to the engine fan, comes from the little black box next to the battery. THere is a 200 amp fuse in there that feeds the tiepoints that I spoke of above. )