Are you buying it privately, if so....it should go for around $16,800 give or take. buying from a dealer, they will probably ask around $19,400 give or take. You should also check out Edmunds, KKB, JD Powers and etc. to get an idea price wise.
Welcome aboard, enjoys surfing the site and good luck.
Is it a certified pre-owned vehicle? If it is, it will carry a 3yrs/100,000 miles warranty and see if you can still bargain it down to 17k out the door. If it's not a certified pre-owned, still bargain down to 16,800 and find out about a Lexus Care warranty....if you plan to keep the car for a while. But if you plan to boost there's no need for extended warrnaty. Good luck!