> Is it important to re-bush the keys or just to rotate
> the metal guide posts that the keys ride on?

At this age it is very important to restore the keyboard and its felt.
Wool felt is just like all organic substances.  It oxidizes and turns
into powder.  If you are lucky enough to find a piano that was spared
the moths eating all the keyboard felt, you will not be spared the
ravages of father time.  Your felt is far more fragile than you are
aware of.  If you turn your front pins it will stop some of the side
to side movement but there is a worn spot in both sides of the bushing
felts in each key.  This will soon be worn through to the wood.  It is
just a matter of time.  Turning pins is a stop gap measure for those
who won't spend the money or don't think the piano is worth it.

Rebushing the keys is not a huge job but in our shop it gives us the
chance to wash the keys and make those black wood keys look virtually
new again.  Just make sure you pick someone who is qualified to do your
bushing.  Nothing worse than a bushing job by an amateur with too much
felt down the hole or too much glue, or too thin glue.  Too much felt
down the hole makes for really sticky keys as does big gobs of excess
glue in the holes.  Thin glue soaks into the felt and makes it as hard
as the glue.  A job with all these problems is worse than leaving the
originals.  At least before it played.

Also, when you bush it is preferred to replace the front rail felt,
center rail felt, and back rail felt.  This calls for re-leveling and
re-dipping the keys using new paper punchings.  This gives you a solid
foundation for regulating the piano action.  If your keys were not
correctly dipped your action could not be correctly regulated and you
would not believe how many piano techs don't even check the dip first.

Of course when you have all the keys and punchings out you can clean
out the mouse nests as well.  I have done keyboards where there were no
front rail felts left.  They were all fluffed up and arranged into a
very cushy mouse nest.  I have also seen all sorts of household items
brought in for nesting material.  One must have been a church piano as
it had Sunday School books shredded and packed under the keys so you
could not move them.

Oh, yeah, I had one piano where a piano teacher used needle nose pliers
to turn the front rail pins.  He did not use the slick jaw type pliers
and the pins all had impressions of the plier grooves in both sides.
This turned all the front rail pins into little files and after a few
years of playing that piano they had not only filed out a hole in the
felt but also a deep slot had been filed into the wood underneath.
Repairs required replacing the wood before we could bush.

Lesson: use the right tools if you turn your pins.

D.L. Bullock
http://www.pianoworld.us/