I would have to say get the 07 monotrial, i have had mine for about a month and i haven't had any problems with it, by far the best disk brake i have had.
Either of the helmets will do you fine but i would have to say get the Giro Xen because it not only looks better than the Giro E2 but it's £10 cheaper as well.
I would keep the maggie and try to set it up good but If you could get a good vee brake then i would have to say get a vee brake because it would save you a lot of hassle.