I replaced the crank in mine just a couple of months ago.
It started out as a deep knocking sound, typical of rod bearings. An initial inspection by removing the oil pan, and a couple of the bearing caps confirmed that this was the case.
When you find out that you have bad rod bearings, you have a choice to make, and that choice depends on how bad the damage to your bearings and your crank is.
If the bearings are damaged, but the crank is in good condition, you can put some new bearings in there, and forget about it for a while.
If the cranks is damaged, it is worth removing the engine from the vehicle, replacing the crank, main bearings and rod bearings. Thats what I did.
I did all the work myself, except installing the crank in the motor. I sent that job out to a local work at home type mechanic.
In total, the repair cost about $1000 including parts, but I replaced some other stuff while the motor was out of the vehicle.
It took about 2 weeks of my time, spread over about 3 months worth of weekends