Greetings Allison:
Well, I'm not sure how successful you are going to be in trying to "sell" the large, mature white pine in your front yard as a transplant. Most nurseries grow their own nursery stock or procure planting material from preferred/specialty vendors (seldom do they purchase large trees from homeowners because of quality control issues).
Might I suggest you contact your local Cornell Extension office for additional information regarding a potential buyer. However, I strongly doubt you will find anyone willing to purchase your tree as a potential transplant. If you really want the tree moved, more than likely you are going to have to pay a certified arborist to cut down the tree; or else, you are going to have to pay a transplanting service to move the tree/roots "in tact", which will be very, very expensive!