Poops

Hi I am new to the site. Recently bought a Discovery, and loving it! However, have a problem with the right rear suspension! It seems to be leaking?? I can raise the rear suspension to off road and it is fine, but as soon as I lower it, it eventually can take a few hours or 30 mins the rear goes down again. Have it booked in at the garage tomorrow, but any advice would be great, as I am not a very mechanical minded woman, and hate to be ripped off at a garage! Thanks