Instigate, document EVERYTHING (you've already started), make a journal of all conversations/visits to the shop. KEEP the oil filter!!!

Then, if they continue to offer nothing,start taking your pictures around to other builders and solicit their recommendations---most, if not all will be quotes to correct the issues.

I predict you are heading to small claims court (that's a GOOD thing cause someone else is gonna fix your mill) and I predict a judge will quickly award the full $1400 back to you. Just my three cents.