removing the spheres can be a big problem unless you use a wrench that is man enough for the job, a strap wrench may not be suitable as I found when I did the same job last year.
A chain wrench is much better if you can find one. I tried everywhere but was unable to find one-even the hire shops couldn't help me-so I made my own. Using a bicycle chain and a piece of steel pipe about 12" long and with an inside diameter of about 1".
Put the chain down inside the pipe until a loop of 6"dia. can be formed, the other end of the chain can be pressed flat against the outside and secured firmly in position using a jubilee clip. And heh presto a chain wrench and I promise you that NO sphere will be able to resist it!.... I even surprised the staff at the 'scrappy' with how good it was.
Good luck mate! BC
bob chambers
January 2010