The exact amount of cap space they need (assuming Kane is LTIR'd or gone) is the caphit of Barron, who's also a RD (which they are in a shortage of, having to play Broberg, an LD, on his offside because of Nurse/Ekholm/Kulak at LD.)
Simplify things:
Barron
2025 5th round pick
In exchange for
Ceci
2025 3rd round pick
2026 2nd round pick
The 2025 3rd for 5th round pick swap is merely due to the Oilers not having a 2025 2nd, and their picks being late round.
Depending on how things go, Mtl can then hope to maybe get another mid-round pick for Ceci at the TDL (2nd or 3rd rounder likely), whereas the Oilers are getting cost certainty for 2 years for a young RD that could still pan out into a 2nd pair role under a new system.
Ekholm Bouchard
Kulak Barron
Nurse Broberg
Multiple mid-round picks are a lot more palatable while getting younger on the back-end to try & keep both Broberg & Holloway, should they decide to do so.