I'm about to replace my radiator unit back up in the van. Before I do so, I
was wondering if there is any preventative maintenance I could do to the
electric motor?  I noticed a labeled, small hole on the Bosch motor.

Could that be for dropping in oil such as?:
http://www.3inone.com/products/motor-oil/

Anything else I should check with the motor prior?

I searched samba, to no avail, and plan to hit the usual vw lists for
advice.