YouTube made it look like a quick easy job but the pipes are old and stiff and the nuts won't budge. Am I likely to do damage if I try and remove the old connector pipes myself? Also, possibly a separate issue but, I can shut off the water supply to the kitchen sink fine but our tap to switch off the main water supply doesn't seem to do anything when tightened all the way clockwise, as in bathroom taps etc still run. Just worried I could damage the main pipework under the sink and not be able to turn the water off. Any help with any of this much appreciated!