Hi there! Even if you’re not weaselproofed, you can’t change the data source – actually, it’d be interesting to know whether you thought you could; that might be something that’s weird or unclear that we could fix!
Anyway, what you’ll need to do is create a new goal with the integration settings you want (the graph doesn’t matter and will be deleted), and then send an email to support@beeminder.com to ask us to switch it over. You’ll need to include the link to the old goal and the new goal – naming it something like “temp-run” will make it easy for us to tell which one is which. 
We’ll switch the new autodata info into the goal, and then delete the temporary one.