as an owner of a E32 1990 and 1989 735iL I know a little about these awesome vehicles. First you have to have a decent wallet, treat them with kindness and the driving experience will be unmatched for the price.
These cars are old and were complicated but surprisingly not overly. The build of the M30 is bullet proof. It is everything else that just wears out but can be still fixed and replaced courtesy of our great exchange rate with the US. Just compare prices of a BMW dealer in Oz with say pelicanparts who I can recommend.
Do your research, do not be afraid of cars that a well looked after, drive them and enjoy! I also own a R320 CDI and Audi Allroad 4.2 so I am a car tragic!