I would resign from this position immediately. First off, credit checks are a breach of privacy and have no effect on whether you are a good employee or not. If you want to blow your salary on hookers, gambling, and credit cards then that's on you, if you show up to work and put in the effort then they should be satisfied.
Speaking of salary, since the author of that email (assuming it's real) wanted to specifically point out how that person is making such a good wage that they can afford a new car with ease, that person should use that to their advantage and find another job. It should be easy if their salary was worth mentioning.
Lastly, the condition and type of vehicle is irrelevant. I work at a pharmaceutical plant in eastern PA, the director of the plant drives a 99 Passat GLS wagon. That car is worth $6k tops, while I know for a fact he makes shy of $400k a year. Some people don't care about cars and see them as appliances to transport their body to work, the one they drive is irrelevant unless they at least imply they're interested in them as a hobby.