I measured a billion times to make sure I had it right before cutting the trim pieces, and then had a bit of trouble getting the rack itself installed -- mine didn't seem to fit (side to side, i.e. the bar was too long) but I used a little muscle power and got the holes to line up and that was that! All-in-all not too bad of a diy installation. It took me probably an hour or two but most of that time was doing all the measuring! BTW -- my instructions were either wrong or the quality of the print was so bad that I couldn't tell if one of the numbers in the measurements was an 8 or a 3! I did my own measuring and realized which it was supposed to be. Just be careful, go slow, and the result will look like a 'factory' install!
One final cautionary note: when placing the racks on the top of the vehicle, it might be a good idea to have a helper or to at least use a blanket or something to protect the paint on the 'other' side from where you are standing. The bars are a bit cumbersome and it would be pretty easy to scratch the paint.