1) I want a white one. Why do some have gold trim but most have silver? Any other car differences other than the color of the emblem?
The trim is a preference thing. Whichever you prefer basically.
2) From a reliability standpoint is the 2WD better than AWD? I never go "off-road" - should I avoid AWD?
I think there would be less wear and tare with a 2 wheel drive as opposed to the All Wheel, but I bought AWD because I live in massachusetts and need it!
3) "Sludge prompt"...is there a definitive way to tell if a car has the problem?
To read more about this topic go to http://www.autonews.com/news.cms?newsId=1534
4) What typically goes wrong with the cars? What should I look for when I am checking out a car? I was going to have a Lexus dealer do their checkout on the car anyway.
Where I bought mine it was a certified pre-owned, so it went through a 124 point check in order to be certified. These cars are extremely dependable and I don't see you haveing any major problems with one. As the old saying goes, "you get wat you pay for".