I've got oodles. Usual thing is they file the tooth down, take an impression and put a temporary cap on it for a week while they make a proper one, then you go back and have it put on. Not specially painful, depending on how much drilling it takes to remove the original. You can also get cerec crowns which are done by computer - he photographs the shape digitally, feeds it into the computer and it's prepared instantly (well, half an hour). Very straightforward but not on the NHS.