My own advice would be to do more (fast) walking than you think you need to. Chances are you'll walk a large amount of the event, and walking at a decent pace taxes the muscles differently to running. It also appears that many of the foot problems people have are because they do lots of running and no walking, and the motion of walking causes their shoes to rub.
I'd suggest doing quite long run/walks for many of your long training sessions (25+ miles ideally off-road, with a mixture of easy-paced running and fast-ish walking). This is a great time to practice wearing a light pack, and it builds up time on your feet which is vital. I don't think sand dunes are essential, but getting off road would be best; and the pack needn't be heavy most of the time.
Of course you still need to build up the running as well, but don't neglect the importance of getting properly used to walking.
Inov8 Roclites are great if they fit you well; I loved mine, but a few black toenails suggest the toe box isn't quite right for me. I then tried some Salomon Speedcross 2's and find them a better fit, really comfortable and just right grip-wise - so well worth looking at. I also tried on some Mizuno Wave Harriers and think they look like a great option too.
What size / thickness of roller do people recommend, as I've seen 4" and 6" versions? After a very painful physio session yesterday I'm planning to get one for my ITB, and I'll probably use it on my glutes, hamstrings, quads and hips as well - anything to avoid the physio's elbows in future!!!