There is a limit on 'gift' declarations. Anything valued more than $60CDN will be charged sales tax, even if it is marked 'gift'. And USPS won't let you insure for more than the declared value, even if it is a gift. Nifty Catch-22.
Pack well, as per your usual standards. The box will receive MUCH more handling than a US domestic shipment, as there will be THREE different agencies involved. USPS, Canada Post, Canada Border Agency, and back to Canada Post. Sometimes, it's a wonder that gear gets through, at all, without a packaging failure.
One tip, make sure that the piece is well sealed, inside plastic. My last two packages have suffered water damage, while they lingered in customs, awaiting clearance. The contents weren't damaged, as water had no effect on them, but I imagine your shipment won't be quite so impervious to water/dirt. Better safe than sorry.