Can a universal condenser fan motor replacement be used with a dual capacitor or do I need a separate capacitor for the fan?

Either one will do the job. If you have a motor with two (usually brown wires) for the capactor then use it.

Keep the other capacitor exactly how is was, except when you swap motors there will no longer be a wire going to the "Fan" side of the cap. If you use two caps then one side will still be common and the other sides will go to fan and compressor, respectively. If you want you can get single cap for the compressor - you will have a wire that is "hot" and one going to the compressor - put one on each side of the cap.

Hope this helps.