Shipping from UK to US

I have purchased a SUT from an individual in the UK, and I will be taking care of shipping from there to me in Texas. The sale was less than $600USD, so I have received conflicting information about what type of documentation I will need to provide for customs. Has anyone ever done something similar to this? Any assistance would be appreciated.
Standard customs form,provided by shipping carrier & filled out by seller/shipper will contain all information needed.As the purchase was under $800.00 there is no import tax.
I bought a pair of Quads from England for more than $800. No problems and no import duty. This was done on eBay.
Ship DHL. Everything DHL from UK is seamless and fast. FedEx, not even close.
Why you care?
It's the shipper's respnsiblity. What you want or paid for is meaningless.
@fuzztone It was our agreement as part of the sale. I solicited the purchase as the seller is a friend of my son.