Does this come with new O-rings or seals?

The condenser ships as an assembly. Confirm whether it includes factory seals by visual inspection upon arrival — if seals look dry or cracked, grab a new set before installation.

Will I need to evacuate the system before swapping this in?

Yes. Your AC system must be fully evacuated and recharged by a certified tech with recovery equipment — this is not a DIY step. Do not attempt to install without proper evacuation.

Are there any mounting brackets included, or just the condenser core?

Assembly ships as pictured — verify bracket completeness before installation. If any factory mounting hardware is missing, source OEM replacements from your dealer parts department.