Back in the day, I lived at sea level and did quite a bit of business in Denver. I was a runner at the time and kept up my routine when on the road. I felt the change in altitude effects, surely, but they weren't debilitating. I now live at 6000 ft and conditioned to that have no issue pretty much anywhere. Flatlanders that visit don't seem to have any more issues than I back then did at this altitude, but often do with exertion at our sites at 9500 ft.

Your 3500 ft change in base altitude shouldn't be an issue. It certainly ain't gonna kill you. Just ride along with any decrease in performance.