I have done it in 3 rooms, and its easy.
TURN OFF THE POWER...AND DOUBLE CHECK IT BEFORE STARTING!.
Theoretically you are SUPPOSED to replace the ceiling boxes with ones
specifically designed to hold the additional weight. Unfortunately that
usually requires tearing apart ceilings. What I have done instead is take
one or 2 HUGE wood screws, at least 4 inches long, and screwed it through
the box, into the stud holding the box. I noticed that when they were
building my house, ceiling boxes were held in place with one lonely nail, so
a additional heavy duty screw or 2, really holds the box in place This also
should be done with heavy lighting fixtures). Its 4 years later, and my fans
are still up, and working, and the boxes are as tight as ever.
I purchased ones with remote controls, so that the little chains (light
on|off, speed,rotation etc) that usually blow around and make noise,
wouldn't be needed. The 1 fan that didn't come with a remote, I purchased a
remote kit for at Wal-Mart, but even inexpensive fans from Wal-Mart now come
with remotes already installed in them. The remotes allow full speed
control, and full dimming of the lights separate from each other, controls
that would normally take specialized additional wiring, inside the walls .2
of my 4 fans are inexpensive no-name Walmart ones ($24.00), and the other 2
are expensive Hunter Douglas Home Depot ones ($95.00). While I am certain
that in the long run, the expensive ones will last longer, I cant really
tell the difference in operation or running noise. Take the time to
carefully balance the blades (by looking lengthways down them from the tip
of the blade, while rotating the blades manually, to look for ones that are
higher or lower than the rest). You will definatly need a second pair of
hands to hold the motor assembly while wiring it into the box, but other
than that its a one man job.
Best of luck