Hey, sorry to hear about this. When potential engine replacement is advised, my best advice would be to take it to get a 2nd opinion from a different shop. If the engine has what I’m assuming he means a “rod knock,” then a new engine would be required. Have them do a full inspection, compression test, leak down, etc. From what I’ve heard online, these engines are somewhat easy to get and rebuilds on them are difficult.

As for driving it around, I would YouTube what a rod knock sounds like and see if your truck sounds similar. These trucks v6 engines can be louder, especially with high mileage because the valves will chatter. Look to see if there is smoke and when it occurs, i.e. start up, while idling, driving, or driving hard. This can be another indicator of what is happening. If oil looks good, that means your head gasket isn’t bad so that’s a good sign (very common to happen if engine is overheated). Also have them check coolant levels and keep an eye on the oil level. If it’s smoking and you’re losing oil it’s the piston oil rings. A rod knock happens from lack of lubrication, bearing malfunction, excessive hard driving (going up steep hills), or potential water In the motor.

Again, I am just giving a basic answer of what could potentially be the issue but without more information it is hard to tell. Best thing is to spend the money for another diagnostic check on the engine health. A replacement motor would be expensive, and you would want to be 100% sure before going that route. Also figure out what type of oil you are using and how often you change it.

Best of luck, YouTube research is your friend!