hey V-
The good thing about Barbs race is that it's run at the same time as the full distance, so you will be one of the first finishers!
I think you'll do fine with a run walk combo. The run course is on cruddy rural roads (not unlike most of nor cal) and has a few good rollers in it. Just plan on walking the hills. It's also VERY exposed, so get used to running in full sun.
But being out in Antioch (my cousin grew up there) you'll be fine.
sigh..
I actually used to live a block off the run course. Vineman is one of the few things I miss about nor cal. I used to run an aid station out on the run course. - And then spent the next month picking up gu packets on my training runs..