A tree 4 foot in diameter needs to be taken down gently to insure that it doesn't crack when it hits the ground. The veneer guys took out a tree across the street from me last year and made a cushion out of the branches of the tree and then dropped the log on to it. Neat trick. Not all trees have good figure or color and that is part of the excitement when you are cutting into one,that rush when you open her up and see something special.You would need to find a bonded and insured cutter in case something goes wrong. This is not a job for you and your buddy if she is 4 foot in diameter. That is going to be one heavy tree and can do a lot of damage if improperly felled.I've cut down and sawn about 25 or so walnut trees in the last 40 years and had pros saw the really big ones or those near buildings.Fun to do when everything goes right!