I'd never try a repair rather than a replace myself. Disconnecting things makes sense of course - though I don't think that applies for the keyboard and mouse.

It really isn't that big a deal, if you've got an adequate external hard drive, and some idea of what programs you've installed, and where to get the makings for putting them back in afterwards. If those are famous last words, my computers must have the nine lives of a cat. They always end up better after a good reinstall, even when they felt on their last legs before it.