No. I hope they were a qualified HVAC technician because they are not a qualified tax preparer.
A replacement furnace or air conditioner condenser can qualify for a 10% credit (up to $300) if it meets the required energy efficiency standards. For this credit, you can include labor.
However, sealing the ducts only qualifies as insulation -- the category is "Qualified energy efficiency improvements" and the description is "Any insulation material or system that is specifically and primarily designed to reduce heat loss or gain of a home when installed in or on such a home." For this credit you can include 10% of the cost of materials but you can't include labor. So, to claim the credit, you would need some kind of proof of how much the sealing materials cost the contractor not including labor or site prep. There is also a lifetime maximum of $500 for all residential energy efficiency improvements so you will need to know if you claimed any of these credits before.
In Turbotax, go to the Deductions and Credits page, look for Your Home, then pick Residential Energy Efficiency credits. Skip the first main section (which is about alternative energy generation like windmills and solar) and the second section will cover energy efficiency improvements like insulation.