I have been mulling over buying a car since I got here in Feb this year, I think I have visited most dealers in Tripoli, the hot spots for car sales are Ashwani Road (called swaney road by ex pats) but excuse the spelling, the other most popular street is 11th June street, there are lots of dealers there, but you don't get any warranty. They only typically drop around 500 lyd off the price if you are lucky, but watch out for ex-pat prices, I have got to know what some models sell for, so if I can help ask away.
If you want brand new with a warranty, your choicen is either Kia Motors on Gargareshb road, or Suzuki on Sal a Eiden Road, there is a chevie dealer accross and up the road approx 2 km from the Suzuki dealer, he also offers a warranty.
Hope this helps
Cheers
Geoff