I had a mobile PC in my taurus for 3 years with a lilliput touch screen lcd monitor in dash, in upstate NY. It was subject to extreme temps all the time, and never let me down. When it's really cold it seemed a bit laggy until it warmed up, but nothing too bad. Sure it's not quite as hot as other places in the country in CNY, but it can easily hit 130 inside a car in the sun, and winters are pretty cold.
Long story short, I wouldn't worry about it.
<a href="http://s35.photobucket.com/albums/d189/mjs3350/car%20computer%20build/?action=view¤t=PA050002.jpg" target="_blank"><img src="http://i35.photobucket.com/albums/d189/mjs3350/car%20computer%20build/PA050002.jpg" border="0" alt="Photobucket"></a>
Sorry for the crummy pic