I replaced the rear struts on my 1998 Buick LeSabre Limited (with Monroe Quick-Strut) but realize that I now need to disable the air ride suspension. Is there a fuse? Or is it as simple as pulling off the little cord connected up there?

Pull the connector. Done.

But you may soon wish you hadn't when you realize rear spring rates on cars fitted with ELC depend on the ELC when there is anything more than a small child in the back seat.

Why do you need to disable the system? The new struts should have the integrated airbags to maintain ELC operation.

Maybe he replaced the air shocks with the shocks they sell with springs a round them?

I am not aware of any coilover setups made for the H-Bodys. Yes, some could be made to fit possibly, but I wonder if perhaps the wrong struts are installed.

Strut masters makes a kit Buick LeSabre Suspension Parts And Kits - Page 1 - Strutmasters

And KYB KYB SR4023 Strut-Plus; complete corner unit assembly Info

FitsRear; w/o Self Leveling Rear
OrRear; For Adapting Air Shock / Strut To Non-Air Suspension

And Monroe Air Shock to Load Assist Shock Conversion Kit Part No. 90007