Unless the card is in a lower grade, you're looking at a $5000-$25000 card.

PSA lists the card at $6500 in PSA 8, even though there have been recorded sales of a PSA 7 for $12k.

It's up to you, but I'd declare the card at Walk-Through tier ($250) for $9500.

The rest of the set would need to be submitted separately, though, since you'd be submitting those at the lowest tier. You could use the Collector's Club Special ($10 per card, min 25 cards) for the remainder (27 cards?) of the set.

If you want to gamble, you could possibly submit at the Super-Express tier ($95) and declare $4750, but you'd be risking it getting lost and only being insured for that value.

If you attempt to submit at any lower tier, PSA would call you to tell you that they have to charge your card for a higher tier, I think. Either that or they'll return the card ungraded. If that happens, I don't know how the fees are refunded.