talking from when i had my 2.4JTD clutch done, i did the following.
i discovered that the stock clutch used and fitted by alfa, is a valeo clutch in an alfa box, which instead of alfa's quote at the time of around £350 to supply only, you can buy for about £150 from a motor factors.
the LUK kit costs about the same and is supposed to be very good too, and like the valeo basic kit, you will get pressure plate and friction plate, but no DMF.
however, because i wanted the car remapped, a Heavier Duty clutch was thought to be the best option, so i consulted CG Motorsport about there uprated clutch kit, which offers about 30% more bite than a stock kit, mainly from a reworked pressure plate, and i bought one of them for just £166 delivered!
(they also do a super heavy duty version with ceranic friction plate too, i think for about £250)
i have a great indy garage, who fitted the kit for just £150 labour, although he readily admits it should have been more, but a clutch job is only worth £200 max labour regardless how tedious it is, so he stuck to his quote and i have been very very pleased.
well who wouldnt be, it cost me just over £300 quid for a better version of what Alfa wanted £970 for!!!
the best part is, whilst the clutch is out, you can manually inspect and check the DMF for excessive play and wear very easily, so best bet is to find an indy that will let you beyond the yellow lines and under the ramp, and you'll soon know if you need to spend more, but if you do most people find a dmf for about £300/350 max.
to know what a DMF should look and feel like, you'll get a good indication from you tube.
search for worn dual mass flywheel or new, replacement etc etc and you'll see the difference between good and bad straight away, so you'll soon know following an inspection if you should or shouldn't spend the extra.
however, once the dmf start to wear you would experience the clutch to feel juddery, and even vibrate in the cabin, as all the torque and engine pulses are transfered through parts of the car rather than being absorbed by the dmf.
if you don't have and juddering, or vibartion, i doubt if the dmf is worn yet, so catch your clutch quickly and you should be good at this mileage at least.