I've tried a lot of the timers/dataacq devices out there from the early days of the GeezCube to the latest thing which is an AiM Solo. I tried Harry's laptimer pro and there are enough quirks I'm selling my 5Hz receiver to another local who wants to play with it. You can create all the sectors you want later for analysis.
http://www.aim-sportline.com/pages/solo/index.htm
First, take an autocross school - its the best thing you can do when you are starting out before you learn bad habits that can take awhile to unlearn.
http://evoschool.com/
Second, take video and data and then try to do the same with someone else who is faster. It's a lot easier to analyze when you have data from someone else and if they are faster its even more useful IMO. If you opt for video, make sure you can see the driver and steering wheel otherwise its just for entertainment purposes.
Last but not least, I don't play with the data or video during the runs as I find it too distracting. I either analyze it after the event or if its a Pro Solo, between the morning and afternoon runs.