I just installed a down pipe back straight pipe not too long ago. Just follow the instructions, I started by unplugging all the sensors first. When you get the rear section off and unbolt the flange in the front WD40 or lube the rubber grommets and use a pry bar to get most of them off, leave one on the back of the DPF until you're ready to lower it. If you're by yourself like I was, I lowered the back end of the DPF monster onto a creeper. That made it super easy to roll the DPF backwards as you slide it out. Oh yeah, a 10" or longer extension is necessary to get the bolts off the flange, the nuts are welded on. I used a pneumatic ratchet. Zip tie everything you disconnected while no exhaust is on. Putting the new one on is a piece of cake.
Hope this helps.