Magento checkout success message help please!

Hello,
I have to change the success message after the checkout on my magento shop but I can’t find where it is this text to edit it.

I speak about this message/notification:

Hello, Jill Macleod

Thank you for your order from Main Website Store (THIS NEEDS TO BE CHANGED TO CRASS & SUGAR PLEASE). Once your package ships we will send an email with a link to track your order. If you have any questions about your order please contact us at support@example.com (THIS NEEDS TO BE CHANGED TO JILL@CRASSANDSUGAR.COM) or call us at Monday - Friday, 8am - 5pm PST. (THE PHONE NUMBER NEEDS TO BE CUT OUT)

Your order confirmation is below. Thank you again for your business.
Your Order #100000001 (placed on May 17, 2011 9:15:16 PM PDT)


It will help very much if you can tell me where I can find this file to edit the text or where in the ACP I can find it.

“Main Website Store” is drawn from ‘Admin > System > Manage Stores’. You need to properly name the store view.

The email templates need to be imported into the Magento admin and saved as overrides for the core files on your server. You should never edit these directly because it breaks when updating Magento. You can edit the email messages from within the Magento admin. If I recall it’s ‘Admin > System > Transactional Email’. Then the settings in ‘Config’ must be updated to use your custom overrides.