My father does this with oak and cherry trees on his property. Try to cut them longer, eight feet is a better length. Once cut to length, find somebody with a portable saw mill. They are like a big band saw. This person can cut them into boards for you. Once you have it cut into boards it will have to be "stuck" - stacked to dry with small sticks between the boards so air can circulate. The person that cuts it for you should be able to tell you how to do it or do a search on the internet. Once it's dry you will probably have to have it kiln dried. It sounds like a lot of work, but it's worth it. I helped my Dad do this to a big cherry, and he used it to make all the moldings for the baseboards, windows and doors in the house he built - it's beautiful.
John