What's my best option when an idiot has blown the turbo on a 2006 Mazda 6 diesel and then continued to drive it until the bearings are buggered? What would be a reasonable price to expect to fix the problem?
If the engine is damaged as you state the best option is probably to buy a sound used engine from a wrecker. Rebuilding the engine could cost $5000, a good used engine should be bought for less than $2000.