Hi, and welcome to the CTD world!
You have many options to choose from, so from that standpoint it's all good. You don't plan on doing much to the truck so stock or a 4" system is fine. The reader before mentioned Hog Performance, I also run their exhaust system and yes it is made of the best matterials arround, 304 stainless steel is used through out the system. The hangers, bolts. clamps are all SS, and the huge muffler is polish to a mirror shine. This is a very good system, and I would call it the TOP of the line in exhaust systems for the CTD. You may or may not want to invest that much in your trucks exhaust system? If so fine they go for around 600-650, which is cheap for the best. Other options would be to go with a 4" aluminized or standard tubing system. Some of the best prices can be found at Summit Racing or Jeggs, they are both very large mail order performance shops that handle diesel truck performance parts. Summit has 4" systems as low as 299. 99 and SS 4" systems for 499. 95, all made to fit your truck. Jeggs has simular systems at simular prices,both are great to order from, and I frequently use them both.
Be prepared for a louder truck, the cheaper and sometimes thiner (tubing) systems allow more noise to transfer to the cab. Also most people that go to a larger free flowing exhaust experiance what is known as DRONE. It's a spot in the RPM range, normally around 2000 prm, that creates a vibration/hum/echo/noise that is much louder then at any other place along the RPM path. This noise can range from mild to down right anoying, especialy it you have a large load or are towing a heavy trailer. I worked thru it, by adding insulation to the cab and installing vibration/heat sheilds along the exhaust system path. The larger exhaust will help reduce EGT's and add's a "performance" sound to the truck. Look around and fine the system that is right for you and your pocket book, good luck.