I am presently flying in the area so my information will be reasonably current. Just keep in mind that just because it was OK yesterday, doesn't mean it will be OK today. I strongly suggest you use a handler, Palm or Universal do a pretty good job. If you don't want to take too much cash with you, plan on contract fuel as the only places I have found that will take credit cards are Luanda, J'berg and Cape Town. Every other place wants cash. You will need over flight and landing permits for just about every place you go. Don't try to BS number game as the fines can get pretty stiff.
About the only places I have found that have radar are Ghana, South Africa and Abuja Nigeria. But keep your transponder on as most aircraft do have TCAS. Some areas you will have to use your HF radio, mostly within the interior of the continent. ATC is spotty, they don't talk wit the ATC's of other countries and in some countries they don't talk to between the sectors. So plan on having to give each sector your complete details on initial contact. Departure point, destination, persons on board, fuel endurance, ETA's, depart time, registration number. If you don't understand something, ask them to repeat SLOWLY. Also be aware that ATC will sometimes give you a fix that doesn't exist on your charts. Be sure to ask them the details.
Depending on the country, the better hotels will take credit cards. So plan accordingly.
Also take some extra supplies with you. Extra oil, light bulbs, various over the counter meds, etc. They will either be non-existent or very expensive.
Be careful when you are give an approach clearance. Some airports, Lagos is a prime example, have multiple approaches with the same name (VOR DME 18R). So it can get interesting.
If you use hard currency, you will definitely get the greasy end of the stick on the exchange rates. Rep of the Congo, the airport will give you 400 francs to 1 USD, but the official rate is 520 to 1. Also the Central African countries that were former french colonies all use the Central African Franc.
Other than that have fun and just watch were you go and how you get there.