The first generation Highlander was sold from 2001 thru 2007. It came standard with an I4 engine, but a more powerful V6 was an option. Front wheel drive was also standard, with an all wheel drive model optional. This was not a SUV designed for any kind of serious offroading; it was more for people and "stuff" hauling.
The trim lines on the Highlander were base, Sport, and Limited. The Sport model was not sold until 2006.
The second generation started in 2008 with the introduction of a redesigned Highlander and the all new Highlander Hybrid. The engine on the new generation Highlander is a more powerful V6. The Highlander Hybrid also gets a V6, but it's paired with a Hybrid Synergy Drive system that allows it to get better fuel mileage, especially in the city. It does not get the same kind of fuel economy as the Ford Escape Hybrid, which is more spartan and lighter in weight, but it does better than the Lexus RX400h.
There are plenty of Highlanders to be found on the used market, although it's still a little too early to find too many of the hybrid models. I usually check on eBay, because they tend to have older and newer models (must be some dealers are using the site as well).