I worked at Sewell Lexus back in '99 for about 6 months as a sales assistant. It was a decent job with good pay ($40K plus overtime), especially for a kid coming out of college with a liberal arts degree.
Back then the deal was you would work as a sales assistant for 12-18 months and then be promoted to a sales person. As a salesperson you would have a free Lexus to drive, free gas, and free insurance. Pretty sweet deal. I was told that the average compensation for a salesperson at that dealership was around $80K, but then again it was straight commission so you had one guy who'd make $200K and another guy who'd make $24K.
As a sales assistant, I was basically a glorified gopher/secretary. I worked long hours and was always on my feet, running around and doing all kinds of stuff. A usual work week was 60 hours. And I had to work Saturdays from 8am to 7pm, which sucked.
However, there were some cool aspects of the job. Many times I got to run errands all over the Metroplex in an LS400 or GS400.
As for the pre-employment testing...I wouldn't sweat it. It's just a bunch of personality-type questions. I'll tell you right now that they are only interested in hiring people who are eager, money-motivated, aggressive, and outgoing...so when you're going through the questions, it should be pretty obvious how you should answer them.
Oh, and back when I worked there in '99, there were about 4-5 female salespeople (all from A&M) and ALL of them were smoking hot. The salespeople in general were very cool -- about half were Aggies. I quit because I didn't want a career in the car business and because working Saturdays gets really old, really fast. But if you're even a mediocre salesperson you'll make decent cash at the place, because almost everyone who walked on the lot was ready to buy. I mean, it's not hard to sell a Lexus to someone. They sell themselves.