A seat, Recaro or Bride seat helps handling a lot as you stay in one fixed position but if you have standard seats and your going fast around a bend your bum will be up against the window lol
All I did was get a fairy bottle and squirt it all over the carpet. Jet washed it for a good 10-15minutes and kept the head of the jet wash close to the carpet to remove all the dirt and left it outside to dry