You know some of the major things. Don't think of it as "knowing what happens."
Think of it as learning "why everything happens."
also agree with Icebird. Having read all 5, you should toootally still read 1.
I hadn't read a book since early high school (12+yrs). Reading these books has really been enjoyable and felt like such an accomplishment.
IMO order of awesome!: 1st place (2 and 3 tied), 2nd place (1 and 5 tied), 3rd place (4)
Tyrion is prolly my fav character, followed by Jon and Arya... but there's so many char's and so much to love (even the things you hate... you love to hate!!)
read them all (and quickly!), you will thank us afterward.