Newbie: addClass problem

Newbie: addClass problem

I have this markup:

  1. <!-- FRAME ONE -->
  2. <fieldset>
  3.     <legend class="some_class">Anbefales</legend>
  4.     <input type="radio" />
  5.     <span>Visa/MasterCard.</span> 
  6.     <div>Some text: 
  7.         <b class="pink">BOLD PINK TEXT</b> 
  8.     some text.</div> 
  9. </fieldset> 

  10. <!-- FRAME TWO -->
  11. <div class="final_radio">
  12.     <input type="radio" />
  13.     Some text
  14. </div> 

There are two radio buttons, sometimes one will be disabled, other times the other will be disabled. I would like to make a script that:
First: Changes the color of surrounding text of the disabled radio button to the color grey.
Second: Checks the other radio button.

This was my plan: I would make a script that:
First: Removes all the current classes and add the class "greyed_out" (or better: change only the color of) the parent element, all siblings and children of siblings (if any) of the radio button that is disabled at that time. 
Second: Sets the attribute "checked to the other radio button".

I made a script, but when I set the bottom radio button to disabled the script doesn't work:

  1. <script type="text/javascript">
  2. $(document).ready(function(){
  3. $(':radio[disabled="false"]').attr('checked', true);
  4. $(':radio[disabled="true"]').siblings().addClass('greyed');
  5. $(':radio[disabled="true"]').siblings().contents().removeClass().addClass('greyed');
  6. });
  7. </script>

Also, is there a way to avoid writing this for each line of code?:
  1. $(':radio[disabled="true"]')
 
Thank you for your time.

Kind regards,
Marius