Replacing shocks on a 1500HD
 

I just got a quote from the shop to replace all 4 shocks on my Silverado 1500HD for $440. I thought I'd save a little money if I did it myself. Is replacing shocks pretty straight forward? I figure, just unbolt the top and bottom, remove old shock and bolt on new. Also, does the truck need to be jacked up so tires are off the ground when replacing shocks? Finally, I've been happy with the stock shocks and only tow a boat weighing less than 3000 lbs and never take the truck off road. So will some KYBs or Monroes from my local O'rielly give me the same or better performance as the OEM shocks?
Thanks