Although the majority of the new government MC's are all BMW, don't count on most mechanics being able to repair advanced computerized vertical twins. The BMW's in use here are generally all boxers which are much more forgiving.
That being said, I've been in Ghana for 18 months with my F800GS and have had no issues. The petrol is much less refined than NA and Europe and as such the local high grade is required to prevent knocking as neither F8 or 650 have ignition advance.
There are a few F650's and F800's here, parts can be couriered in for less than purchasing locally and as VanGS has noted, Tony Togo's KTM is right next door and his team has a good reputation for service.