Welcome from Wilmington, NC.

3) where can I get a complete new radio antenna assembly?

Check on Ebay ---http://www.ebay.com/itm/AM-FM-RADIO-STUBBY-ANTENNA-BASE-FOR-VW-PASSAT-BEETLE-JETTA-GOLF-GTI-MK3-MK4-/232463665336?fits=Make%3AVolkswagen%7CModel%3AJett a&hash=item361fea08b8:g:vjIAAOSw1aFZjhl8&vxp=mtr

might have to change the connector but it an exact replacement.
There are many listings, just used this one for reference;