Here is some info I hope helps you
Vaccinations-
you really need to speak to your doctor as I've no idea what you've had.
Yellow Fever is mandatory
You need anti-malarial
I have also had:
tetanus, Diphteria, Polio, Rabies Hep A, Hep B, Meningitis.
Can't remember which (o think it's polio) which 'clashes' with another vaccines so can't take them all together.
of course, the only mandatory one I know of is the Yellow Fever one. Other vaccinations are a matter of personal choice /risk taking etc
(some drink any water/others are more cautious!)
Carnets: Embassies will state that they are mandatory for Mauritania and Mali. Some Overlanders who have been before report that this is 'hit and miss' and you can get through without- nothing is ever guaranteed!
VISAS:
2 needed
Mauritania (obtainable in London from a very helpful lady called MMe Assoul at the Embassy of Mauritania, 8 Carlos Place, Mayfair, London W1K 3AS tel: 020 7478 9323 - can be done by post too - or get it in Casablanca.
You will find the Mauritanian consulate at 382 route d'El Jadida, in the Quartier Beau Sejour. The opening hours of the consulate are: Monday to Friday from 8.30 AM until 3 PM, Friday from 8.30 AM until noon. You can call the consulate at 02 223 73 73. The visa costs 200 dirham (US$ 20). You will need to bring two passport sized photographs. If you file your application before 9 AM, you should be able to pick up the visa after 1 PM the same day
Mali get it near the frontier.
Insurance - Green card for Morocco - third party only from your insurers- or can be bought in Tangers.
Further south.....you're on your own

might have to buy 'insurance' but prob. not worth paper it's on!!

- you might want to speak to more experience people who have done this trip before.
Festival
Ticket costs €300 and isn't negotiable! provides entrance, food water, Touareg tent and mats and I think that's it!
web site here
www.festival-au-desert.org
TIME
Good question! no idea but allow certainly 4 weeks. Not exactly European roads from what I have read up to so far. Buy Chris Scotts' book Sahara Overland- very informative.
Money
Sadly needed!
Moroccan Dirham, Mauritania Ouguyia and Mali CFA
Understod to need about €2000 to cover food, camping, fuel, some 'hotels'
Charity
If you'd like to contribute to worthwhile work, then I'd encourage you to donate as I do to
SOS SAHEL. Helping with access to medical/water cleaning/engineering/urban development. etc etc.
They are on the web.
Distance
Depends on how many detours and how long is a piece of string!
Count (probably) on 10,000Kms maybe a few more
GS's...rid'em beyond the M25! ;0)