with difficulty if they are anything like mine. The theory is that you remove the spring clips with pliers and drift them out using a lump hammer and a suitable drift. In reality they are prone to seizing up and sticking solid. Try cleaning all the old grease off and soaking in top quailty penetrating oil. Apply frequently with a toothbrush all round the hinge pins, leave a few days and repeat as many times as neccessary untill they free off. failing that you need to drill them out and replace with new ones. Hard to ger to with a drill though.
graham
May 2008