What level of rider are you?
If you don't think you will be a front runner and are doing it because it's a dream, then you can get away with less tyres than that.
I went out on Day 5. I was still on my original tyres from the start but needed to swap the rear that evening.
Michelin Deserts, and not spinning up the rear.
You will need to take tyres/mousse with you and arrange for someone to carry them.
Leads me to;
What brand of bike do you think you will be on?
KTM have had (I assume still have?) a service where you can buy an option to purchase parts from their vehicle when needed, and if you buy your tyres and mousse from them, they will also carry them for you.
Obviously you won't get it from them unless you are riding a KTM, and they need to be Rally models.
Spare wheels and trunk/s are carried by the organisers.
This info is based on it being run the same way as in 2006.
The best advice I can offer, is ride slower than you think you can to avoid injuring yourself and damaging your bike.
Once you are injured, the lack of sleep from trying to do your own maintenance will compound your issues enormously.
Nobody is going to notice the difference if you are running at position 183 or 129 or 97 etc.
You will though, when you hurt yourself.
It's a tough race. It's even tougher when you have to maintain your bike yourself.
Be the turtle.
You'll love it