Replacement crystal on Uno for cold temperatures I want to run an arduino out in the cold (-40), and use the serial communication - I believe that the crystal is the weakest link (the one for the serial chip) - however I don't see any drop-in (through-hole) replacement crystals that would work in such cold, so would a SMT version work instead? if so, which one would be possible to solder (package?), and do I need to change the caps to match? 

P.S. - Yes, I could heat it/insulate it, but that comes at a fairly high power/complexity cost
There is a solution for just this problem, it's a "crystal oven". It is used to keep a crystal at a constant temperature so that the oscillating ferquency remains very stable.

Crystal ovens are usually expensive as they are quite precise and have good insultaion, but here's a kit that you might adapt for your uses: http://www.minikits.com.au/Oscillator-Heater, or google around to see if you find something that might suit you better.

You could also consider making a heater with a simple temperature regulator of your own to keep the crystal warm  (many temperature sensors for Arduino are available on the web).