I have had my done twice. Cost has been about $800 if I remember correctly.
It is a DOC/DPF filters in that can. Check around, various companies have the cleaners that are required. Call around and check. Some of the large trucking companies with their own in house repair technicians have been buying and installing the cleaner machines. If you find someone who works where there is one, you might be able to get it done at a "discount".
The HEST light, when does it come on?? Is it on all the time or flash on and off ocasionally?? Mine would go on when braking hard and quickly and coming to a stop and putting the parking brake on. Found out that it is a warning light that the DOC/DPF are at a high tempature and they don't want you stopping to quickly around material that may catch fire at the exhaust pipe end.
If you take your DOC/DPF apart yourself, be very careful. Once we did ours the second time after it plugged after a few thousand miles, you may be needing injectors for that Cummins. And that gets expensive real quick as we were forced to replace all of them.
