Change the injectors on a bmw - 1998 BMW Z3 Roadster

This is not a job for the untrained or inexperienced. The system stores high pressure fuel which has to be taken care of. There are cleanliness issues to address, engine needs to be clean. All areas of connections, pipes etc need to be clean. There maybe special tools needed. You don't say why you are changing them, if the servicing has been done correctly they can do 150k with no problem. You will need a manual to ensure all steps are done properly and safely unless you have experienced help.