hey,all you need to do is suck out all the old fluid from the can,and i highly recomend using lucas racing products power steering fluid,its fine for all applications,thats what im using,my pump was making a whining noise and it took away the noise,they really use high end oils and polymers,lucas oil products are one of the top products you can buy,i know how mercedes emphysizes greatly in the owners manual the need to use all mb products but theres no need.pick up lucas power steering fluid,one bottle will do the job its about $7.99 at autozone,unless you really wanna go nuts and replace more fluid than whats in the pump.