How much time and money will this most likely cost me?

My vehicle had no warning or engine lights but was in need of an oil change (not low on oil) and had been making a slight ticking sound. I started it one day and got it sounded like it was idling high then I got a warning that said “power reduced to engine” then it died and would not ever turn over or start again. A mechanically inclined friend did some work on it based off the codes it through. First he changed the oil, then replaced the high pressure fuel sensor, then the high pressure fuel pump. Still no luck. Another friend looked under hood and all but one rocker arm on intake side were broken. I still owe over $5000 on this car so I’m wondering if what to do. I really afford a mechanic. My credit is not that good as it is and I’m tempted to just self surrender the car back to the loan company.