If you wish to conduct adjustments on your own TGB 303R 125 then it is usually a good idea to have access to a Workshop Manual to use as a reference just in case you want to know easy methods to take out a certain part much like the Door and match it again successfully.
TGB 303R 125 Workshop Manuals gives you targeted diagnostic details for the vehicle therefore if something is not working it helps you determine what the problem is and tips to resolve it. You will be able to evaluate if this can be achieved yourself or in the event the job is simply too big you can make a reservation for your 303R 125 into a nearby car garage.
TGB 303R 125 manual