There's no guarantee that the service department will be cluey enough to deal with the DPF anyway, these things are a mystery to many but you could ask them - likely they'll do a forced regen which will cost you at minimum an oil change + labour (about 4 hours). There's no indication that this would fix anything if the DPF light is out. Does the DPF light and CEL (Check Engine Light) work when you turn on the ignition (not starting the car)? If so, the car doesn't think there's a problem and there probably isn't (with the DPF).
The sluggishness might be from something else. There might be an issue with the turbocharger (commonly a cause of sluggishness). Check the turbocharger actuator hosing (the thin black rubber hoses that lead to the gold circular widget on top of the turbo). These often crack, come loose and start leaking. Even close examination of the hose doesn't always reveal the problem because it might just be a slight hardening of the inner part of the hose, which stops the rubber from sealing against the attachment. Follow this all the way back over the engine to the right-hand-side of the motor where the vacuum pump is.
Lastly, don't just drive along at a decent pace then stop and turn the engine off. The hot turbocharger will start cooking the oil within its bearings, and since the engine isn't running the oil won't be replaced or cooled - it will form hard deposits (sometimes referred to as varnish) on the bearing surfaces which will lead to the destruction of the turbocharger.
Clicking sounds are normal from metal cooling from a high temperature, DPF or not. Getting it hot enough like that, and shutting down quickly to hear the clicking, will give rise to the aforementioned turbocharger failure. Save yourself that cost and let the turbo cool (idle the engine for 1-2 minutes after a hard run) before shutting it down. Turbo timers are absolutely invaluable if you're in the habit of doing this, although losing a turbocharger from this would be a quick way to break that habit!
