I've had a Surface 604 since April 2016 and have put 950 miles on it so far...
I did order the front shock. Shock was back ordered, so the first 400 miles were with rigid front end.
My counsel is to spend the $400 and get the front shock. Suspension was a noticeable difference...
I also added...
Hi here's a link to some mud flaps I have on my fat bike.
If the link is bad, just google Dave Gary mud flaps
Hope this helps...
https://allseasonscyclist.com/2013/02/06/daves-mud-shovel-fat-bike-fenders/