I have just come back from a trip Amsterdam- Bamako and sold my car in Mali. Selling it was no issue at all, we got asked 50 times a day if the car was for sale.
The questions they tend to ask, give a good impression of what they want:
Is it a diesel? (they strongly prefer a diesel)
Is it a manual? (they want manual, an automatic breaks down too quickly)
Is there airco? (they want airco, but if there is none its still ok)
Is it a 4 cylinder? (They prefer the 4 cyl because it consumes less)
They dont want a turbo or an injection. They want carburators, because they are more reliable and easier/cheaper to fix.
They prefer the 190d, because 'everyone has a 190d', but a manual 4 cylinder 200d will sell just as good. Just to give you an impression: we bought our w124 for 1600 euro and sold it there for a 1000 euro more.
I posted a vid on youtube
YouTube - Sahara Overland with Mercedes
or my blog with car pics
p.p.s. I would not go for a different car then a Mercedes Benz. By no means a volvo, I don't think I have ever seen a volvo in Mauri or Mali.