First things first, ARRIVE EARLY. This is 300,000+ people coming into one area so imagine the traffic around Columbus on gameday but literally 3-4 times as much. Traffic gets bad starting as early as 7-8am so the earlier you get to the track the better, and it is more than acceptable to be at your tailgate drinking after 6 (at 6 they shoot off a cannon to let you know the gates are open and wake everyone in the sleeping areas). Also stock up on alcohol and a cooler Saturday night, Indiana finally has Sunday alcohol sales but not until noon on Sundays so that won't help you at all on race day.
Never had a parking pass so can't speak to that, but every house in the neighborhood sells parking in their yards and its always worked great for us. Again the earlier you get there the better choices you have (find the ones who rented porta pottys for their guests), and just make sure they have a plan not to park you in but most do a good job with that.
Also have always sat in the infield so can't help with seating, besides bring good sunscreen or hat cause there's little to no escape from the sun in the seats. As for the infield, turn 3 is the party area where the real heavy drinking and partying goes on, but it's crowded and you have to get there overnight to be in line for a great spot. Turn 4 is a little more relaxed and has better views to actually watch some of the race, but can still get plenty of drinking in there too. No matter where you sit a walk over to turn 3 just to see it all is worth it during the middle of the race in my eyes.
Lastly either be prepared to race out of there as soon as it ends to beat some of the traffic, or bring supplies to tailgate after the race. We've been able to sneak out immediately after the race the last few years and got home quick, but if you wait too long all of the chartered buses start coming through and they block up everything around the track for quite a while.
Any other specific questions let me know, this is the first year since 2010 I'm going to voluntarily miss it (missed twice when my wife was 9 months pregnant with each of our kids).