Most Lowe's Stores have grills for sale that are already assembled and ready to take home and use.
However if you do buy a grill that is not assembled yet and it's a larger size grill then yes Lowe's will assemble the grill for you free of charge.
Also if the grill you buy is $499.00 or more then Lowe's will deliver the grill to your home for a short distance free of charge otherwise you can either take the grill home yourself or pay a delivery fee.
But yes Lowe's does offer free assembly for full sized large grills but you can usually find lots of grills at Lowe's that are already assembled and ready to cook on.