It is worth while doing tbh especially on tourings due to being slightly heavier, the swap itself will not be hard to do as its only removing old discs, calipers and carriers and replacing with items from 318is. The brakes shall need to be bled then also so think about doing a set of braided lines while your there and have the lines disconnected. Also check rear metal brake pipes for advanced corrosion as if these need to be replaced then now would be the time to do it as your only bleeding the system once then.