If you want to undertake maintenance on your TGB 203 then it is usually a great idea to have access to a Workshop Manual to use as personal reference just in case you need to know the best way to remove a particular component for example Exhaust and install it again efficiently.
TGB 203 Workshop Manuals can offer you detailed diagnostic details for your vehicle therefore if something is not working it helps you understand what the problem is and easy methods to fix it. After that you can decide if this can be done on your own or that the job is simply too big you could make a booking for your 203 in with a decent repair garage.
TGB 203 manual