Updating Rockbox

Hi, it’s me again!  I have a refurbished Zip installed with up to date Rockbox and I am pleased with it.  However someone suggested that I update to the latest development build as it has a number of enhancements such as better battery life.

Now, I bought my Zip with Rockbox already installed so don’t know if it was installed with Utility or manually.

Can someone kindly advise the best way to install (or overwrite) the dev. Build on to the device and point out any pitfalls?

As ever, your advice is much appreciated.