Dealership Withheld Purchase Paperwork On A Used Car; Just Discovered Online Proof They Hid A Known Blown Head Gasket. Location: Mt

Location: Montana. 2 to 3 months ago, I purchased a used black 2017 Honda CR-V from a major dealership lot here.
I have two major issues going on that I need advice on:
1. Withheld Paperwork: When I left the dealership, the finance team did not give me copies of any of my signed paperwork—no bill of sale, no retail installment contract, no finance agreement. The only thing I have is the physical "As-Is" window sticker.
2. Hidden Mechanical Defect (Fraud): The car just suffered catastrophic engine failure consistent with a blown head gasket. While looking into my options, I found a public Google review from another customer posted 4 months ago about this exact same black 2017 Honda CR-V at this specific lot. In the review, the customer details how the dealership's own service department told her the car had a prior $6,000 head gasket failure and ongoing issues, which they tried to rush-sell to her before she backed out. The dealership owner replied to the review, confirming they knew exactly who she was.
The car is completely dead, and I am on a very tight budget and cannot afford to fix a major engine failure that the dealership clearly had documented prior knowledge of.
Since they completely withheld my mandatory transaction documents (making it impossible for me to verify what waivers or disclosures were legally executed in the contract) and they actively committed fraud by hiding a massive mechanical issue they had clear records of, what are my next steps?
Do I go straight to the Montana Attorney General’s Consumer Protection Division, or do I need to hire a private consumer rights attorney? Can an "As-Is" sale be voided if there is public proof of prior knowledge/fraud?