Hi John,
I've used the technique Geo describes, lopping off the rubber button that keeps the bushing in place. An Xacto works, or I've used a drill bit. Next apply lots of silicone or WD40, then push it out with a large pipe as Larry suggests.
It's possible you'll still find the bushing stuck, sort of adhered to the inside of the column. I recall using a hacksaw blade carefully to split the bushing lengthwise, to loosen a badly stuck bushing. Just be careful not to scar up the inside of the column.
The large pipe also works to press the new bushings into the column. Lubing the rubber helps them slip in a little easier, try WD40 or even lighter fluid. I'd not use silicone spray when re-installing. You want something that pretty thoroughly evaporates in time, to leave the bush snugly in place.
Alan