Bought car from a private party. Driven car 5 times in 11 months.

2 out of 5 times it wouldn't start after driven to market. Purchased new battery, no change. Now, no start, no power, steering is locked, brake is locked, no dash, windows are stuck down. Had towed to dealer, they couldn't figure problem out or diagnose, and they had car for over a week. Dealer finally suggested to replace J519 module for $1,700.00, but they were not sure if that would fix problem. We can't afford to replace module, especially if that doesn't fix problem.