I'd take a few days and wisely use them to really get a grasp on what you want the rifle for and what configuration you want to buy. Definitely read and understand the AR Primer sticky. Read through the threads that discuss brands and make your own decision on what's as good as.
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together.
US Army 1966-69, VFW Life Member, Retired Geek