all depends on what you want to do with the tree. If your looking to just get rid of it..any tree service company worth their salt will gladly take it off your hands in exchange for the wood as payment. Right now, good walnut is at a premium.
If you are looking to harvest the tree for yourself, you'll be looking at doing a little bartering. Around here (SW Pa.) there are alot of guys who will come out and cut the wood onsite with portable mills. Some go by the hour, typically around 75 per hour others will work something out in return for a share of the wood. Some mills are willing to go as far as to wheel and deal on a start to finish kinda deal, take the tree down, mill it and dry it in return for a larger share of the wood. I'd make a few phone calls and see whats available and what is practical in terms of costs to you.
"..... limited only by imagination"
"Just smile and wave boys, smile and wave"
Skipper the Penguin