Achieving the H-mark – What should you know?

Hello oldtimer fans, I own a BMW 3 Series, built in 1989, of the E30 series, which is to receive the H-mark in the context of its new registration this year. What do I need to know about this? The vehicle is (except for the radio – to which suitable original replacement is sought) in absolute original condition. Currently the technology is completely repaired to reach a HU without defects. Since the BMW is a reimport, a full acceptance must be made to my knowledge anyway.1) How verh Does this happen with the H acceptance? Does the vehicle have to be presented to an inspection centre or can the examiner carry out the necessary examinations etc. in a car dealership?2) Does anyone know more about this? Who has experience with an H acceptance and can give me and interested readers good tips and hints?