Lifter/cylinder springs bad

CarolinesMom04

I have a 2015 Denali, has been well maintained. Other than AC compressor, DVR replacement, and tail light assembly replacement, nothing notable ever as far as under the hood maintenance problems w the engine. 2 weeks ago, I took it into a shop, reputable place. The phone charger hookup fell back into the dash, and I told them to drive it for me, I was noticing it riding rough, couldn't put my finger on what it was. 1 week later, they told me the vehicle was ready, that the tires just needed rotating. Again, nothing funny happening with dash lights or anything. Not even a full week of having it back, I heard a noise, I thought on the passenger side while in motion, 35-45 mph. 10 min later, I was pulling over to a home depot parking lot, not sure I would make it there. The car was jumping, and and coughing, I couldn't get much speed, but when I pressed the accelerator, it got me there. I had it towed back to the same shop. Now 5 days later, they indicate they had an older model do this same thing, that 2 of the cylinder springs are bad, and that it takes 11 hours to replace them, and they can't guarantee the motor isn't shot, and that's a 12 hour job. So I'm taking the chance of incurring a much heavier bill if I don't go ahead and replace the motor. Again, no dash lights ever came on during this episode either. Thoughts?