Springs,How much would it cost to convert a 98′ range rover from air suspension to spring suspension?

I'm considering buying a 98' Range Rover for 1100 the body is clean the title is clean the interior is clean. The owner says the car runs fine, but the suspension is dropped. Mechanics recommended switching to a spring suspension to avoid future maintenance problems with the air suspension. I just want a rough estimation of how much that would cost… parts & labor. There's also a leak from the "front seal" in the engine. How much would that be to fix
My car has an automatic transmission.