Pull the dividers out ?

Yes

Thanks.

Question #2 - in order to change out the stem, do I need to fully recable (mechanical shifting)? It looks like that's the case but want to confirm.

Edit: looked closer and yes, there's one cable going through the stem... but it's probably the front brake which is much simpler to deal with (just disconnect the wire from the wedge that's it, worst case you need to replace the front brake cable if you can't get it back in the wedge because it's too frayed)

This was super helpful - thank you. I'm going to be a nuisance and ask one more question. I bought the bike with the consideration of upgrading to electronic, so figure I'll ask about preferences between eTap and Di2 (likely Ultegra vs Dura Ace). Pros/Cons, especially if trying to do this one on my own (limited wrenching abilities).

---
I have SRAM eTap now (only the rear brake cable in the frame) so I can't confirm but from the service manual diagram it looks like the cable housing is not going through the stem so you should be able to just remove the bottom basebar bolts out and leave everything else connected.
I replaced by headset bearings and I took the whole fork out without needing to do anything with the brake cables.

https://trek.scene7.com/...t_Service_Manual.pdf

Keep eTap off TT bikes. You can make the extension buttons and derailleurs work but the junction box is very hard to place well, the satellite buttons are ridiculously big and non-aero and of course the integrated PM is stuck with pointless tiny chainrings

It's still a big lump of plastic exactly where you don't want a big lump of plastic. Disturbing what is pretty clean airflow over aero bars and levers with a tape on lump is a clear loss when we're all looking for small gains. I've had quite a few clients with eTap and was open minded when first encountering it and like the idea of wireless shifting but it's just clumsy and the whole shrinking of cassettes and chainrings just when everyone is going in the other direction is really bizarre