NaturalScorp

Hello All - I currently have a 2000 VW Passat Sedan and I want to upgrade to a Lexus IS250. I'm looking to purchase a 2008 or 2009 and would like some advice on what I should be looking for. A navigation system is a must and low mileage. As you can probably tell, I don't have a clue about purchasing a used car. Please help guide me in the right direction. Thanks for your time, NaturalScorp