Hamish - if you use bipolars then you don't have to worry about direction. You could do a lot worse than a pair of Rubycon CE or Nichicon Muse bipolars.

Remove the op-amp board, taking care to cut the gunk holding it down to the main board. Then fit a cap to the top two holes and another to the bottom two holes of the left socket, leaving the centre hole empty.

Take care to mute or set the volume to minimum when you start running music, then you'll be ok once the charge on the caps is constant. Leave at least 48 hours before starting to listen seriously. That's 48 hours of music, not standing idle. You can leave the amp turned off.

This way, you've done no damage to the Caiman and can put it back the way it was at any time.