Check ash load with VCDS:

  Control Module ->
    01-Engine ->
      Advanced Measuring Values ->

LocDescriptionDataNotes
IDE 06059Particulate Filter Oil Ash Massgrams
IDE 06060Particulate Filter Ash Load Limit80.00 g(probably)
IDE 00433Ash VolumeLitersLiters? Really?
IDE ?????# of requested regensI can't find this

DPF part number

DPF part number:  04L-131-670-GX
Costs about $1,050 plus core ($200 core charge)
One source: vwpartsvortex.com

Links

(just for reference)