For my 300CE stored as yours will be, I:

1. Increase tire pressure to 40psi (minimizes flat spots).

2. Full tank of gas (minimizes water vapor in tank).

3. Isolate battery (however you want), and hook up smart battery maintainer to it (keeps battery charged).

4. Open container of DampRid in interior.

5. Cloth bag full of Moth balls under hood (repels mice). Also place one in interior and trunk only if you strongly suspect mice will be hanging out in that garage.