If I don't want to teach, is there any reason to get a PhD?

I've been told that if I don't have an undergrad degree in CS, there
is no chance I can get into CS grad school [at school Y].  Is that
true?

Did you experience any gender discrimination in grad school?  If so,
how did you handle it?

If I want to work in industry, is there any difference between the
jobs I can get with an MS and those I could get with a PhD?

What was the biggest mistake you made in grad school? [Or if you could 
do one thing different in your grad career, what would it be.]

If I want to work for a few years [join the peace corp]/[have a family]
and then apply to grad school, could I get in?  What can I do to
maximize the chances of getting in and being successful?

I was told that you have to know what area you want to study and who
you want to work with when applying for grad school.  Is this true?
What if I'm not sure whether I want to study graphics or databases or
theory, should I even be applying?  What if I change my mind after I'm 
admitted, am I stuck?