I kinda jumped into this without doing a lot of homework (though I've made BD for a year for my '84 Mercedes 300SD), so I don't know what I should be doing to the Jetta. Previous owner is a diesel mechanic, so I know it's been maintained, but he knows nothing about BD. What needs to be addressed for a car like this when switching to B100? Any good VW forums you'd recommend?

I've had great luck with my '87 Jetta (with '91 1.6 turbo motor) on B100 and SVO (two-tank system). The braided hoses between the injectors began leaking, so I changed them to a biodiesel-proof Tygon. I changed the stock hoses between the filter and IP for Tygon while I was at it. That's it. No other changes. Performance is just fine as long as the weather is warm enough for the biodiesel to stay liquid. My soy-based biodiesel clogs filters below freezing, so in winter I run biodiesel in the heated "svo" tank, and dino-diesel in the main tank, switching as soon as the IP reaches 0C. One tank of diesel lasts all winter this way.

Yes, there are some excellant VW forums here and on the web. The forum search function will find too many to list here. I recommend finding someone nearby to visit who has the same car. They'll also have had time to find the best local VW resources.
Cheers,
JohnO