NonprayingMantis: I would do this:
Advise your manager verbally as soon as is reasonablly possible - this gives you an opportunity to discuss replacements, training, etc.
then when you write your resignation letter it is just a formality and will only need a couple of lines as per nzkc's post above.
at a large corporate your manager will have people leaving and starting all the time - it won't be a major issue for them and they will normally be absolutely fine with it.
johnr:Kiwipixter: Also, the resignation is usually acceptable via an e-mail but?definitely?not via txt.?
Surely no one would do this!