For me when I went to the notification bar and click on the message notification, it gave me the option to choose which client to open it with and if you click the check button first it'll set that as the default.
As for the double ringtone, I'm not sure about the other one but with mmsblur installed, open up Text Messaging, hit the menu button, messaging settings, and uncheck the notifications bar. This will disable the ringtone and vibrating and such.
As for the double ringtone, I'm not sure about the other one but with mmsblur installed, open up Text Messaging, hit the menu button, messaging settings, and uncheck the notifications bar. This will disable the ringtone and vibrating and such.