Self Supporting Antenna Tower Maintenance

I have a friend who has a Rohn self-supporting antenna tower (like the one pictured) with a directional cellular antenna at the top. The tower is probably 40 feet high and was erected by a previous homeowner. They would like to make it useable again but the antenna needs to be turned to point at a specific cell tower.

The manufacturers documentation indicates that the tower is climbable but I've never dealt with these towers and thats outside my expertise. Who would I even call for that type of job?