Tires

At 32,000 miles the old tyres are likely to have far less tread than a new tyre. I If the left/right balance is upset, then if you have a need to do an emergency stop, it could be enough to cause you to loose control. I would replace two tyres.

Now you have two new tyres and two older tyres. You want the new ones on the back. Yes on the back. In that emergency stop you want to keep the back end in the back, but if the front tyres are holding better, then the tendency is for the back tyres to loose traction and swing around to the front giving you no chance of controlling the car. Hopefully you have never and will never experience this, but do put the good tyres on the back.

This can be serious in the summer, but in snow or on ice, it becomes much more likely to create a serious safety problem.

just depends if thread depth is close to new tire? Or... maybe it's time for the other tire to get a hole in sidewall!

Yeah I think what I'd do is if the spare is full size, put the spare tire and a new tire up front and then throw the used-but-good front tire in the trunk as the spare.

Hmmmm I'm not so sure I agree w/this. We're talking a front-drive car here so the weight, turning forces, and drive power are all on the front tires placing more stress and wear on them than the rear tires. Front-drivers are notorious understeerers too and not overly prone to oversteer. Since the fronts wear faster than the rears on all front-drivers, the logic above (best on back) would dictate that you would never therefore rotate the tires on a front driver...you would wear out the fronts, then move the rears to the front, and buy new ones for the back. We all know that isn't the case.

IIRC we're talking about a late model Passat here...a car likely to have ABS and possibly even stability control. It's already designed to help you out quite a bit. I'd keep the best ones on the front where the weight is and let the car deal with the rest.