Hello

Thanks for your question.

From what you describe it does sound like the top portion (scion) of your tree may be dead.  Have you gently scraped the bark off of some of the branches that appear dead?  If you see a layer of green cambium and/or there is still some pliability (bendability) to the stem, it may still be alive.  Have you watered your trees?  They are going to need at least 1 inch of water per week, i.e. approximately 10 gallons of water applied around the base.  It is also helpful to apply a 6 inch layer of shredded bark around the base and not against the trunk of newly planted trees.  If you provide the necessary water, the trees might recover next year.  You might want to wait and see before removing them and replanting.  We do suggest that you prune off the suckers coming from the rootstock, i.e. below the graft line, as these will not produce the kind of peaches that will be produced on the top portion. 

Here are some additional 'growing peaches and growing fruit' resources from Extension:

https://extension.unh.edu/resources/files/Resource000586_Rep608.pdf

https://www.canr.msu.edu/home_gardening/fruit/