As Caine says make sure the engine is cold before you remove the hose. You should also loosen and refit the radiator cap and/or coolant reservoir cap before removing the hose to make sure there is no residual pressure in the system.
You will spill some coolant so cover anything you dont want to get wet.
If the old hose wont come off just get a knife and cut it lengthwise at the connections.
Brian.J.
August 2008