Whatever flight option you get, make sure it's routed on one of the European carriers. Might as well read the fare rules and score a free (or discounted) stopover in a hub city like Frankfurt or London.

I haven't been to ACC since I lived there over 8 years ago, but that is what I did every trip instead of flying direct from the USA. Hung out in London for two days in between BA flights. Saw Amsterdam for 3 days thanks to KLM. Only cost me $75 extra. The service on the Euro carriers is usually better anyways.

http://wikitravel.org/en/Ghana has good basic info, and you can branch out from there. Things may have changed, but any problems with officials were usually easily handled by a small bribe, if you aren't morally opposed to such antics.