First, I'm going to refer you to the US CDC's Health Information for Travelers to Ghana. Read the whole page; there's lots of useful info about health in general.
Then, to the UK Health Protection Agency's Guidelines for malaria prevention in travellers from the United Kingdom. Scroll down to "Chapter 7 - Special Categories." That has a whole section on long-term travel & expats. A bit technical.
Mefloquine (Lariam, Mefliam, Mephaquin), doxycycline and Malarone are all effective throughout Ghana for preventing malaria. There are pros & cons to each one. One issue for a long trip is availability and cost. Malarone is the most expensive and you will not be able to get it in West Africa. Doxycycline is the cheapest and is widely available. Mefloquine is in the middle--I have heard that yo have to hunt around a bit to find it in West Africa.
In terms of which one you should take, here is my usual mantra: There is no single best antimalarial. The best one is the one that is best for you, considering your destination, your health history, your allergies, your age, your gender, and, sometimes, your pocketbook. There are pros and cons to all the effective antimalarials. Someone else's experience cannot be used to predict how you will respond ot a given drug.
It's something you really need to discuss with your own doctor.
Hepatitis A is always a great idea. It is spread thorough fecal contamination of food & drink and you have no control over who has been handling your food and how meticulous they are about handwashing.
Hepatitis B is spread by body fluid contamination. There are other issues for Hep B besides getting, um, very well acquainted with local people. It can be spread if you have to get medical or dental treatment and the provider isn't meticulous about sterilization. Some people get it if they will be going to a country where the blood supply is not screened for Hep B, just in case.
You can get He A & B separately or in a combined vaccine.
Typhoid is always a good idea. It can be hard to diagnose and there is a lot of drug resistance. There are two vaccines available in the US--a shot, good for 2 years and an oral vaccine good for 5 years. (You may hear about a combined typhoid/hep A vaccine. It is not available in the US.)
You should absolutely be up-to-date on polio. If you have not had a booster as an adult, you should get one. Thanks to the polio problems in Nigeria, there are sporadic cases all over West Africa.
Meningitis See this thread. Meningitis Outbreaks in West Africa. Even if you will be based in Cape Coast, there is a good chance you will do some personal travel or meet someone who has meningitis.
Ghana requires a yellow fever certificate of all travelers.
No one, even a total couch potato, should be without up-to-date tetanus immunization.