I am planning to buy a preowned 2014 or 2015 model S and I've spent hours over the past few days searching the nation for available cars. There are a few features that are very important to me, such as autopilot, the power liftgate, homelink, and turn by turn navigation. Obviously autopilot was available as it's own package, but it seems like some other things such as the power liftgate were available in both the tech package as well as the premium lighting and interior package. It also seems like at some point along the line turn by turn navigation became a standard feature, but I don't know when that happened. In addition to my confusion about not even knowing which packages were available at which times and what packages had the options I want add the fact that many non tesla dealers don't even know what options the cars on their lots have. A few have access to the original window stickers, but in many cases they have nothing. I'm getting ready to pull my hair out here trying to find a car with everything that I want and I don't want to assume that a car has something it doesn't and wind up regretting a $60K purchase. Is there any good historical list of what packages have been offered over the years and what features those packages included?