Hey Kimanchi, if you wanna practice for your trip, try driving round the M25 10 times on the trot. If the Landy makes it, you'll be fine! The most boring bit of the trip will be the 2,500 miles down the coast from southern Morocco through Western Sahara and into Mauritania on the tarmac. Good thing is that that part of Africa is full of Series Landies for some reason. Plenty of guys who can repair your Landy when necessary, plenty of spare parts and cheap labour to keep your bonnet polished.
Re equipment, don't get carried away (as we did!). A spare fuel tank will be a good idea - keeps the weight low/frees space. No problems about quality of fuel if you stick to the main petrol stations. Err, something to make tea/coffee, a tool kit and your Haynes manual and you're set.
Of course, if you try and get to Timbuctou in the rainy season - best thing is to pick up a mate (and his 4x4!) on the way to pull you when you're stuck. In the dry (Dec-March), you'll just need a soft cushion to sit on and those ear defenders!
There's a couple from Sheffield that have just passed through here (Ghana) in a 2CV that got em down here no problem. Bloke last year came down in a Renault 5. Or, you can do like me and have loads of fun spending lots of money on things you'll never use.