Wheel well liners are a definite yes - they provide protection and also make the truck look complete. Just look at one with them and one without and you will see what I mean.
5th wheel/gooseneck prep kit is a definite yes - even if you never use it, it will help at resale time and the cost to get it from the factory is cheap compared to having it done aftermarket. You may not want it but the next buyer probably will.
I went with the XLT Premium package because I was trying to maximize my payload but if all you are hauling is a pop up camper then that is not a big concern. It has all of the amenities I really care about and none of the foofoo ones I would never use. My previous F250 was a Lariat and I did not use a lot of the things it came with on a regular enough basis to want to have it again.
Adaptive steering, BLIS, etc. for me are not necessary items. I like the back up camera (when I don't have the camper on since it is in the tailgate) and that is good enough for me.
I had an F250 with the 6.2 and 4.30 gears whereas my F350 I drive now (truck in signature) has the 6.2 with 3.73 rear end and to be honest, I am not unhappy at all with the 3.73's. Since you are ordering the truck, get the 4.30's but since I have had both, don't believe the rhetoric about how huge the difference is between the two because it is not that big.
