[SS10] Mill-Resurface template assistance?

I am working on a resurfacing project where we are not doing any slope correction. We are simply grinding off the top couple inches of asphalt and laying back new.

I'm getting a little confused on whether I need to create a milling component or an overlay component, or both. Basically I need a component that will follow the existing surface on the top, and follow the existing surface a couple inches down on the bottom.

Is that Milling? Is that an overlay? I've seen a few posts here about this sort of thing, but none of them have answers, so I'm mystified.
I have both Geopak and InRoads, but the Openroads tech is the same in either.

Thank you.