Panic is starting to set in...

My liquid diet officially starts on 1/12.  I went out tonight to start shopping for my supplies.  Walked into GNC....and I was completely lost.  I just stared at the shelves...one, not knowing what I was looking at and...two getting blown away at how expensive everything was.  This is the same dilemma that I always face.  I don't know how to find the right foods, supplements, etc.  And when I do...I hate paying so much for them!  I'm so afraid that if I don't have several weeks planned out that I will find surely flounder after my surgery!  I need help!!!