I would like to save the pachysandra and vinca (and hostas and daylilies too, but it'll cost more to replace the groundcover, I think).

If I dig them up in the week before they start work, I could replant within two weeks, which would be the third week of october.

I know that's probably too late for them to get established before cold weather hits (MD zone 7). Is there any way to overwinter them, like in boxes of damp peat moss in the garage?

Recognizing that I am in a warmer zone, I've planted or transplanted all manner of hardy plants throughout winter without problems. In zone 7, it is unlikely your soil freezes to any significant degree and that should be the only limiting factor in planting these groundcovers this late in the season.

Now i just have to get pscyched for all that digging. I used to garden a lot but haven't much in the past 9 years or so.