Congrats on the new truck. I would really like to have a new Chevy but my '08 only has 36,000 miles on it. They have really beefed up the specs on your truck and it will be a superb tow vehicle for Suites. Mine is great - yours will be that much better.
By all means get the bed sprayed before adding the hitch. I have Linex and very pleased with it. Very rugged product. There are bedliner cleaners that make it look like new if it gets dull. About an hour of work applying it and it looks like new.
I use and recommend
Husky Fifth Wheel Base Rails and Brackets. They are very rugged. Unless you are very mechanically minded do not attempt to install the hitch rails yourself. They must be placed precisely (slightly ahead of the real axle centerline) to maintain the right weight distribution in your truck. Get an experienced installer to do that work. It may be necessary to drill holes in your truck frame and you want that done right the first time. Make sure you and the installer have the same understanding as to how the hitch will be installed before the work is done.
The risers or spacers from TrailerSaver come in 2" or 3" heights. You will need the 3" at least. I wish they would make a 4" riser. I had my trailer "tubed" at Mor/ryde and that raised the trailer 2". We extended the gooseneck to fully extended position. We are level and have about 5" clearance above the bed rails. I would like to have 6". If I fabricate a new riser (spacer) to 4" I can raise my axles 1" by using the auxilliary mounting holes. Note that I have Mor/ryde IS axles. Have not found a need to do this yet. If I get into a place where I need extra bed clearance to get into a site (there have been a few) I can add air to the Trailersaver and raise it to over 7" above the rails. Have had to do this 3 times in 3 years. The 5" clearance has not been a problem travelling on the road. It is only in unusual situations that more clearance is necessary. Make sure you have a 12V compressor available to add air to the hitch. A small inexpensive Canadian Tire unit works for me. Similar products available at Harbor Freight or auto part stores.
What are you doing for a brake controller? If you ordered the truck onboard brake controller option it can be used for the Suites electric/hydraulic disk brakes with the addition of a module available from the brake actuator manufacturer (Dexter). I had to modify the wiring in my truck in order to use a 3rd party brake controller (PS3). At the time the module to use the onboard controller was not available. The PS3 has worked well for me.
You have done a good job researching and asking questions. You will soon be rewarded with great times in the new rig. Enjoy!