Do I need a vacuum pump and refrigerant to install this?

Yes. The system must be evacuated by a certified technician before removal and recharged after install. This isn't a DIY task — take it to a shop with AC recovery equipment.

Will this work if my original condenser is still holding pressure?

The condenser must be replaced as part of a full AC service flush. If your system failed, debris or moisture is already in the lines. Replacing just the condenser without flushing the system will compromise the new unit.

Does this come with new O-rings and fittings?

The condenser assembly ships as-is. You'll need new O-rings, seals, and possibly receiver-drier or accumulator gaskets depending on your shop's service protocol — confirm those with your technician before installation day.