Getting the old bushes out with a saw is possible, but will take some time.dubaidrift said:
Getting the new ones in without a press, is less straightforward. You could try using a hammer, but will run the risk of damaging the bushes if not perfectly straight. A heavy vice might suffice, or you could use a 'bushwacker', essentially a piece of threaded rod to pull the bush into the arm.
But easiest would be to just find a place with a press, only takes a couple of minutes.