Next time the key won't do anything in START, try this - without letting the key all the way out of the START position, wiggle it slightly and see if it will kick.
Just about every ignition switch I've seen fail has usually failed in the START position first - the reason I didn't bring it up that way was because I wasn't sure what you were talking about at first (believe me, when you're trying to get people who aren't there to help you diagnose a problem, it's far better to have too much information than not enough information - when making a diagnosis, I know I'll ignore anything that doesn't relate. But, if you didn't give me something I need, I end up having to wait after I ask - which delays things.)
Replacing the ignition switch is more of a pain than anything else - if you feel the top of the column down by the firewall, to the right of top, you should feel the thing. Usually, there are two screws that hold it in place and a single large electrical connector. Just make sure you don't misplace the operating rod (down from the mechanical lock where you put the key) putting the new one in - it's usually all done with the key in the OFF position.
Probably a half-hour or so - longer if you're a large individual (like me.) When working under the IP, I invariably find the work easier if I pull out the driver's seat - which is probably why I don't like power seats (I can have a manual seat out in three minutes. Power takes considerably longer.)