As the clutch is so new, it must either be a faulty clutch disc (i.e. diaphram springs broken/not giving enough pressure when released) or an oil leak, saturating the clutch plate. Either way its a gearbox out and job new clutch plate needs to be fitted. (unless you hold car at lights on clutch ALL the time and generally abuse it to the extreme ofcourse, but i highly doubt you could give it enough abuse within 5k to make it go so soon.)
If its an oil leak, make sure you fix this first, as the new clutch will only slip again if the leak still exists.
If its the coil pack o-ring, you must be loosing alot of oil through it to leak into the bellhousing and comtaminate the clutch, its more likely to be the crankshaft seal behind the flywheel. The seal itself is pretty easy to replace, but involved removing gearbox and flywheel to get to it.
Take it back to the mechanic who changed the clutch for an inspeaction.