Depending on your route, I'm not sure where you would actually expect to meet big dunes which you "have" to cross. YOu can travel through alot of West and Central Africa and not come across any big dunes. There are quite a few small dunes but you don't even need to go over these. People take battered old 2 wheel drive cars and get through so a Rangie would have no problems. Whilst one can get into discussiones on whether its better or worse than other 4x4s, it shouldn't have any problems in terms of capability.
Also there seems to be suggestions that the Sudanese border with Chad will open again. The European Embassies often seem to give out more negative information than what is actually happening there. Keep an eye of the other posts.
If you do want to ship, probably going out of Ghana, Togo or Benin are probably your best bets. I've heard of others shipping from there. Also heard of others shipping from Gabon and Nigeria but they seemed to have more problems. I haven't shipped from there, we drove through in a 110 TDI Defender, so just going on what I heard other travellers say.
[This message has been edited by Toby2 (edited 16 July 2003).]