Welcome to the forum Rob, what do you have in mind? Are you looking at replacing the seals in your leaking steering box or replacing the whole box with a recon one. The second is the more expensive but only needs to undo a handful of nuts and bolts and getting the pitman arm off can be a bit cheeky but certainly do-able for most people in a couple of hours, personally I've never rebuilt a box so couldn't advise but do a search in the defender section as I'm sure others have