You can always switch back (and forth) to the old theme during the transition. So, no harm in testing it and see how it goes.
Save and download a copy of your existing setting for good measure.
Make sure to install both the Xtreme Theme AND the Xtreme Theme support PLUGIN.
The plugin will give you access to the legacy admin that mirrors what you had in the 2010 version.
Then activate Xtreme and select a sub theme that is the closest to the look you have now. Check things out and come here if you need help to finalize the look under Xtreme.
And if it takes too long and you don’t want to leave it under Xtreme until you have time to figure things out, you can switch back to 2010 temporarily.