Where are you? In the west? In the east? These matter because of humidity and geography. Sequoiadendron stands a better chance in the west. Zone 6 is not really a border zone, though, the tree should be fine so long as it is planted in advance of temp drops to help it get established a bit before winter. Salt lake city is technically zone 6, maybe even 5, and there are 30 ft tall trees here. If you want to baby it, do what you can to shield it from harsh drying winter winds and full winter sun.

West coast- but in the mountains. Dry air, yet plenty enough moisture in the ground.
Moderate winters, plenty of snow, 1-2 really cold snaps.
We DO get cold windy days.

I'm thinking if I can help it survive one winter, it has a significantly better chance taking care of itself following years. Just not sure what I can do for a 10 footer(mechanically).

Is this something you have to take now. The nursery won't hold it till spring?

If it's now or never plant it and forget it. The sooner the better.

Good luck.

Dave

Plant it, the sooner the better. If you can shelter it a bit from the wind, whether its with a house or another tree, the better. You should be fine, this species does better in places where there is not much summer humidity, that's why I asked about climate. So long as its not 105 degrees and 15 humidity, no harm in planting it. Just water it.