How reliable is full engine replacement?

Engine replacement these days is getting more and more common cause quality control is gone. Make sure they are putting in a NEW engine, yes 0 miles, and not a remanufactured or a used engine. That is up to you make them do what they say they will do.

Since this is a warranty repair that you're not paying for let them replace the engine. Read your warranty booklet and see if you're entitled to a free loaner vehicle while yours is in the shop. Keep all receipts and documentation for future reference if something isn't right after you get the vehicle back. Another thing to keep in mind is that typically the warranty coverage continues from the original date and mileage. It doesn't reset to the beginning of the warranty period. For example, if you bought this vehicle brand new in December of 2018 and it came with a 5 year or 100,000 mile warranty, you still only have two months left on the warranty coverage of the new engine. You don't get another 5 years or another 100,000 miles. Same is usually true with an extended used vehicle warranty. So, with that in mind, if it were my vehicle I'd waste no time trading it in, somewhere else, when I got it back! Hope that helps! Jim