Suspension

I have a '92 Deville and the air tubing that is used to pump up the rear suspenion has a leak. The leak in the hose is behind the dash somewhere. I felt that it would be alot of money or a lot of work to have this repaired. Can anyone give me any advice on this ?
I was also thinking of giving the caddy a higher ride, like you see with the Chevy, Caprice or Malibu. What would I have to change in order to do this, shocks, springs, etc... please help.

I'm sure replacing the coil springs would beef up the ride height.I could be wrong, But I've never heard of air suspenstion lines going through the dasboard area.