BMW 503 Workshop Manuals
If you want to undertake adjustments on your own BMW 503 then it is usually recommended to have a Workshop Manual to keep just for reference in the event that you want to know easy methods to strip off a specific part such as the Gearbox and install it again accordingly.
BMW 503 Workshop Manuals can provide special diagnostic info for your vehicle therefore if something is playing up it helps you figure out what the problem is and how you can resolve it. After that you can evaluate if this can be done on your own or in the event the job is too big you can actually book your 503 right into a nearby friendly mechanic.