Tree Specialist?

[masswich.livejournal.com]

I have a Norway Maple in my back yard that is fairly old and showing some signs of wear. My usual tree guy, who is pretty good, was only willing to do some basic trimming on it because he worried that it was too prone to cracking if he climbed around on it too much. He recommended removing it and replacing it.

I know its basically a weed but its the only big tree in the yard and does provide some nice shade. It will take 20 years for a replacement tree to get anywhere near as big. Does anyone have a tree preservation company they can recommend for me to get another opinion from? I'd love to be able to have someone make a few key trims, perhaps from a cherry picker, fertilize it if necessary, and buy it a few more years before the inevitable felling. Or at least I'd like to know that its time has truly come.