Sleep Training an Infant ... Might Be The Hardest Thing I've Ever Done!

I am a wife and mother of a 5 1/2 month old little girl!  I never thought I could love someone as much as I do her!  I've had others tell me that you don't know what love is until you've had a child and I could empathize with that, but the real feeling - WOW - it's one that words can not describe.

I am going to Vegas in a couple of weeks for my cousin's 21st Birthday and I will be leaving my little precious girl home with her daddy for almost 4 days.  (Anxiety!)  My husband is a wonderful father, but I'm so emotionally connected to her and it will be very difficult for me to leave her for that amount of time.  I've also spoiled her badly and let her sleep in bed with me, co-sleeping is what they call it, because she loves it and honestly I do too.  After 9 months of having her in my tummy it was very difficult to leave her crying alone, plus I'm a big snuggler.  Not to mention the added (selfish) bonus of nightly feedings just rolling over and letting her eat and fall back asleep.  Now though, we have reached quite a dilemma ... how will she go to sleep while I'm gone?

So, It's 11:15pm and I am listening to her scream from the other room as if she is in horrific pain.  I've been doing this for an hour now and I don't know how much longer I can take it.  I've been in there at 15 minute increments to try and sooth her and give her a binky and talk softly to her, but she just keeps screaming.  I don't know how other people do this!  As a mother we want to protect our children from any type of pain and although she's not experiencing any physical pain she is in deep emotional pain.  When I've gone in there she's shaking and crying SO HARD it makes me cry!  At daycare they are able to lay her down in her pack n play (which I have her in) with her soft blanket and they say she might cry 5 minutes and then she'll go to sleep.  Huh?!  I'd like to know their secret!  I've read several studies on the effects the "cry it out" (CIO) method have on babies later in life and their findings come back with little to no difference in other sleep techniques psychologically.  I'm not sure how to take that long term information and make it make sense in the short term.  Ugh!  Can't do it any longer, I've got to go get her and sooth her!  I failed at this technique.