I think that you are talking about the swivel base. I had to pull the drivers side seat on mine because Thor had a spacer in wrong and the seat had a wobble to it.
The bearing assembly can be replaced without replacing the base as the whole bearing assembly is by itself and sandwiched in between the frame the seat bolts to and the pedestal.
There are 4 bolts that hold the seat to its frame. Don't confuse the bolts with the track bolts. The seat bolts or rather nuts will be the four outer bolts. There is a stud in the center of the pedestal held with a slotted nut and a cotter pin to lock it in place. "Looks like an axle stud and nut".
Remove the seat by removing the four nuts that hold it to the track assembly, lift the seat off the track assembly, pull the cotter pin out of the slotted nut in the stud that holds the track assembly, remove the slotted nut and lift the seat frame/track assembly off of the bearing. Then you can lift the bearing assembly off.
If you can find all the ball bearings, you may be able to repair what you have.
Actually, it sounds as you might have a spacer in the wrong place on your bearing assembly too cause I don't see any way that those ball bearings would come out unless it was put together wrong like mine was.
2017 Thor ACE 27.2