a leopard can't change its spots	used for saying that someone will never change their behaviour or character
all mod cons	=all modern conveniences=the machines and equipment in your house that make life easy
break the mould	change situation by doing sth that is very different what other people usually do or have done
change your tune	change your opinion or attitude
have a change of heart	change your opinion about sth or decide not to do something you were planning to do
know sth inside out	be very familiar with sth
reinvent the wheel	waste time and effort trying to do sth that someone else gas already done well
stick to your guns	refuse to change what you are saying or doing despite the opposition or criticism of other people
the tools of the trade	the skills and the equipment that you need in order to do your job
turn over a new leaf	change your life by starting to be a better person or stopping a bad habit