Those who love circuit bending know it can be a dark art to start off in - but seasoned modifier Look Mum No Computer has new starters covered with a recent live stream of him bending the Yamaha DD-5 Drum machine. In the stream, he goes over what to look out for, how to add an LTC pitch changing module, and explains his process throughout - with minimal electric shocks! There is also some live ebay bidding and discussion of e-auction best practices.
See part 1 of the live stream below:
And here is part 2, where he finishes the job:
Always take care when circuit bending as it can be dangerous - and as Sam mentions, only bend a piece of gear you can accept may never function (at least in the same way) again. Many of us have learnt this the hard way!
For a detailed review of the DD-5 on it's release, see this link from muzines: http://www.muzines.co.uk/articles/yamaha-dd5/107
Look Mum No Computer has a wealth of resources, projects and superb oddities over on his website: https://www.lookmumnocomputer.com