Are there any specific issues I should be concerned about in buying a used one w/175,000 miles on it?

Don't do it! I just answered your other question about the airbags being deployed on this Volvo. I had an '06 Volvo S40 and I can personally tell you that repairs on this European car AREN'T cheap. Plus, with mileage THAT high + damage it sustained, you're looking at a money pit that you REALLY don't want to be in.

Duck and RUN! With the residual value of he car, the damage is very severe to warrant a salvage title. There is likely no way to get that car completely back to the way it should be, and repairs to them are EXPENSIVE. So expensive I would never consider owning any Volvo, no matter the history.

I agree with most of these guys, just walk away. If the air bags have been deployed then that alone is costly enough. I'd look into your states DMV laws before going to far.