Magnolia tree

[newgirl68]

Hello,
I have a beautiful magnolia tree in my front garden but it has now got a bit out of control, hanging over the pavement etc and needs to be cut back. I have been told that magnolia trees don't take to being cut too much. We have only lived in the property for 15 months and I don't know when it was last cut. Does anyone know at what time of year they should be cut/pruned?
Thanks

Also, my husband said he would do it!! But would it be better to employ a professional? I was thinking maybe there is a certain technique and would hate to kill it!!