I was in a similar situation yesterday. we look at the comsumer's reports and there is really no mention of trans problems or sludging. So, we went to Pohanka Lexus dealer in Chantilly Va. and bought a certified 2003 RX300 with 58K miles on the clock, 3 years/100K miles warantee, for $22,250. I suffered from buyers' remorse as well, but I got over that when I start to drive the car. From my limited experience about engine sludge, it seems it can be prevented by regularly changing the oil and use synthetic oil for it, as the previous posters said, which I always do in my cars anyway. You can pull the valve cover and look inside the cam housing for thick, heavy, black craps. For the trans problem, that's why I got a certified RX300 for and I do intent to change the trans fluid every 15000 miles. Congrats on the purchase and don't forget to enjoy the car. You'll get more of your money's worth out of it that way. Andy