I wouldn't be too worried about a small residual of vinegar. You can take a heat gun to it if you want to make sure it's really dry. I'm sure that's good enough, but if you're really worried you could wash it down with another solvent, or gasoline. Just don't do that while you're smoking.

As in the post above, you can plug in the sender underneath the car and take the opportunity to calibrate it to your gauge.