How do I replace a screen with the exact same screen?

Hi there,
I’m completely new to this kind of thing and have been learning from tutorials online, but so far have not been able to find any that relates 100% to my current task.
What I am working with is a simple 2 sec handheld shot of a phone. After being colour-corrected with Magic Bullet, the reflective screen of the phone has rendered the digits unreadable. I still want to keep the Magic Bulleted effects for the remainder of the clip, but want to garbage matte the original screen over the top of this clip.
So, through the tutorials, I have learnt how to X-spline and track, and add a surface. I figure, there must be some way to essentially reverse this process (or invert, rather) so that I can use the original non-MB clip and track the screen. Seeing as this is the same clip, motion would be already synched and I should just be able to lay the screen over the Magic Bulleted whole image. Maybe I don’t even need the surface thing for the MB clip, as I’m just laying the cut-out screen over the top…
Can I do all this in Mocha itself, or do I export it to AE?
Instructions worded for an idiot would be much appreciated thanks! :stuck_out_tongue:

Yes, that is what I theorised ay be possible. But like I said earlier, I am a complete beginner to mocha. How do I achieve this?

Can you just use an inverted matte in AE from mocha?
Cheers,
Mary