Upper Control Arm bushes.

I have a '97 EL, with lowered suspension. About a year ago a mechanic
friend replaced the Driver side Upper Control Arm Bush. the same
problem has occured, this time on both sides. My friend said that this
is a common problem because of the extra work put on the control arms
because of the lowered suspension. A few questions:

1) is my friend right, is this going to be a recurrign problem.

2) Are the bushes easy for me to replace myself? I'm not a mechanic,
but can have changed brakes and done some minor mechincal work on my
car successfully before.

3) If it is too big a job, how much should I be looking to pay?

4) If I can do it myself, does anyone know where I can get Ford parts
at a reasonable price in the Sydney area?

Hope you can help!