Anyone climbed Ben Nevis?

[vrsmxtb]

Doing a charity climb of Ben Nevis at he end of May, it's one of the sunrise ones, so leaving at 2am! I believe it's about 12 miles in total.
Has anyone done something similar before? Just how strenuous is it, and how much training should be put in. I walk fairly regularly. Also what is the bare minimum outdoor gear I will need, other than good boots and a waterproof jacket?

[vrsmxtb]

No this is my first one! I'm not sure which route, I'll have a look through the briefing e-mails.
Yep, I sweat quite a lot when I exercise so will invest in some decent underlayers.

[vrsmxtb]

Thanks for the advice.
This is a group ascent so I assume all organised and guided in terms of navigation. I'll go along to my local Cotswold Outdoor and tell them what I'm doing. I'm also hopefully sailing the Hebrides on a wildlife research boat the week after so some of the kit might match up for that.