I dont know what "Monroe replacements" are, but if they are standard type shock absorbers, they will fit you RIviera.
Autoleveling system consists of air pads that sit on top or above your socks. They are filled with air when you car is loaded, to raise the rear and level it out.
I dont know why you dont hear them working or are unsure, but when mine are on you can hear it and rear passenger feels the vibration
perhaps somethings wrong