user7317: A little background:
I need to generate a 40KHz frequency as accurately as possible.
(One of my other posts is here: 
Stable frequency generation)
My code is solid- I'm using an Uno R3 and generating the most accurate frequency I can at this point. The only way to get a more accurate frequency is to upgrade the ceramic resonator to a crystal oscillator.
So, my over-arching question is: How do I actually upgrade the ceramic resonator to a crystal oscillator? 
Things I'm considering are:
Is it worth it to actually upgrade my Uno R3 - and is it even possible? Is there a clone that drives the ATMega328p with a crystal oscillator that I could use instead? Is there simply just a better model for this application?

user8613: It's really easy to take an ATmega328 chip and wire it up on it's own.  There are even instructions on the Arduino site on how to do it.  Take a look at http://www.arduino.cc/en/Main/Standalone .
You could even pull the 328 out of the Uno, add the crystal and a few caps and then program it with the Uno board.  I've done this a few times myself and it worked just fine for my needs.

7317: <p>A little background:</p>

<p>I need to generate a 40KHz frequency as accurately as possible.</p>

<p>(One of my other posts is here: 
<a href="https://arduino.stackexchange.com/questions/8671/stable-frequency-generation">Stable frequency generation</a>)</p>

<p>My code is solid- I'm using an Uno R3 and generating the most accurate frequency I can at this point. The only way to get a more accurate frequency is to upgrade the ceramic resonator to a crystal oscillator.</p>

<p>So, my over-arching question is: How do I actually upgrade the ceramic resonator to a crystal oscillator? </p>

<p>Things I'm considering are:</p>

<p>Is it worth it to actually upgrade my Uno R3 - and is it even possible? Is there a clone that drives the ATMega328p with a crystal oscillator that I could use instead? Is there simply just a better model for this application?</p>
 8613: <p>It's really easy to take an ATmega328 chip and wire it up on it's own.  There are even instructions on the Arduino site on how to do it.  Take a look at <a href="http://www.arduino.cc/en/Main/Standalone" rel="nofollow">http://www.arduino.cc/en/Main/Standalone</a> .</p>

<p>You could even pull the 328 out of the Uno, add the crystal and a few caps and then program it with the Uno board.  I've done this a few times myself and it worked just fine for my needs.</p>
