Do I need a new receiver-drier when I install this condenser?

Yes. Anytime you open the AC system, the receiver-drier absorbs moisture and needs replacement to prevent compressor damage. Replace it at the same time as the condenser.

What tools do I need to swap this in?

Standard socket set, refrigerant recovery equipment (required by law), and a torque wrench. You'll need to discharge the system before removal — this is not a DIY-without-tools job.

Will this work if my original condenser has a small leak?

No. If your old unit is leaking, replace it. A damaged condenser means refrigerant loss and moisture in the lines, which will ruin a new compressor fast.