It is cake to replace the tumbler. You need a u-shaped wire which you can actually fashion yourself out of a coathanger. You turn the key to position 1 (or 2, I forget) and then push in the wire firmly into the two holes until you feel the click, and then the tumbler comes out. Search the archives, but don't delay the replacement. Once the key won't turn it's a major PITA.

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Prost!