I think i had had to carefully remove my rubber seals from the old injectors, much easier with a drop of oil, as long as they are not split or damaged they should be fine. After the fuel lines have been disconected from injector you are left with an 8mm bolt that fastens down the injector retaining clamp. Your old ones may be seized in but if your buying new ones dont have to worry about damaging thread. Got my bosch units from andrew page, cost me around 70 quid there are no copper washers to change.