It's pretty easy. You may want to check that the back plate has holes in the right place for the new board (or you get a new backplate to match it). Also make sure your PSU plugs into it, that you have the right sockets etc for all your other devices. And, a clean installation of Windows would be good too. Doesn't the 845GL include onboard graphics? You may need a new graphics card if the new board doesn't have OBG.