If you wish to conduct maintenance tasks on your Suzuki GSX R 400 then it is usually a great idea to own a Workshop Manual to keep just for a reference in the event you want to know the way to take out a particular component such as the Door and fit it again in the right way.
Suzuki GSX R 400 Workshop Manuals will provide you with exact diagnostic wisdom for the vehicle therefore if something is playing up it can help you understand what the issue is and tips on how to repair it. You will be able to analyse if you can do this by yourself or in case the job is too big you are able to make a reservation for your GSX R 400 into a suitable garage.
Suzuki GSX R 400 manual