My car (BMW 316i E36)just developed a problem and and I know next to nothing about engines so I need some idea so I know what I'm facing (and budgeting for). The car no longer engages gears when the engine is running. When the engine is off I can engage all the gears but once I start the car it can't engage any gear. I have so far been told it might be that there is a leak on the hydraulic system of the clutch. Any second opinion on the solution (and possible cost) will be appreciated.