dont worry about warranty.I had my gooseneck added by my Jayco dealer when i bought my 321rlts.
I have a real truck bed,8ft,
,so I dont know about your clearance but there are some adapters that have an offset at the ball and have seen one that offsets high.
I wouldnt go to a regular 5th wheel hitch but each to his own.I have the old style "flip over ball" since my truck is 03 but next one will have the "turn over ball" that takes no space in the bed and if later you dont like gooseneck there are 5er hitchs that drop in the hole.