Crawler that tracks dates and prices on two sites

Hello. I want a crawler that copies all the information from these three "cars for sale" web sites. [login to view URL] [login to view URL] [login to view URL] I want to add another one later but it is a harder site to work with. This crawler has to search all of the new cars and all of the used cars at the end of each day (Australian time). What I want it to do in particular is keep track of - What date a car is listed - What date the price changes - What date any other information changes - A history of the price - What date the ad was taken off the site - A copy of the ad I need to be able to see the car on one of the above sites, and then come to my site to see the history of the for sale ad. I want to know if the car has been for sale for a long time. And I want to know what the price was originally, and what the price is now, and how long it took for the price to change. To help do that I want the number of days to appear next to the old price each time the price changes with some text that says "This was the asking price for [number of days] days". It should also have the total number of days the add has been active next to the listing date. I am not too familiar with crawlers so do not know what to specify. Feel free to ask questions. I also want to be able to search on the same criteria, and filter the result the same way as on [login to view URL], and also view the pages the same. I am guessing the crawler will pick that all up automatically. Thanks