K.,
You've read it: excessive water on the brain isn't good.
Likely you've read it: a shunt implanted will help drain the water away.
There are a whole bunch of horror stories and success stories to go with all that reading.
Bottom line - she won't get better untreated.
Go in armed with information AND questions. Get all of your answers up front. Find out where you can get more information if you don't quite understand something.
Don't freak out. Get informed!
Also: find out what to do when the shunt gets plugged (and very likely it will).
Learn infant/child CPR and what to do (and not do) if your baby/child goes into convulsions.
The more informed you ARE, the less you will freak out - which is what your baby needs most from you.
Also: be careful of hydration. Don't go over. Don't go under. You'll know what I mean awhile after she's had her operation.
I would be happy to know how your little girl pulls through with this.
Blessings and prayers for your little girl! I think she'll turn out okay after surgery. :) She's got a concerned Mom!
Take a deep breath, and research only short time during the day (this includes sleeping time!) You will not help anyone by being short of sleep during this time (well, beyond normal waking up for baby at night!)
Good luck!
M.