We took out our old furnace and installed an outside wood boiler that has a radiator type unit with a squirrel cage fan to force the air through our old duct work. My question is can a central air unit be added somehow?

Yes

Just install as you would normally with the A/C coil in the air handler duct work. See Google for examples.

Yes, but you would need to know the amount of cfms your fan was pushing.