can you bust a wheel cylinder changing the brake shoes?

You don't 'bust' a wheel cylinder, which is cast from steel, but you could dislodge the piston inside and possibly damage the rubber seal in pushing it back, if you were to say operate the brake pedal while the brake shoes were removed.
Most cylinders are cheap (£5-£8 each) and if the car is over 10years old it's a good idea to replace them anyway.

Georgioblu
September 2006