Did I ruin my engine ???

'02 2500HD 4x4 with 6.0L gas engine.

Inadvertantly put in about 5 gallons of old, yellowed gas from another
vehicle that had been sitting idle for about a year. No doubt had water in
it too.

2 days later, the 2500HD wouldn't start in the morning and making very scary
($?) clanging noises. After many, many attempts, truck finally started.

Truck runs fine now (still sometimes hard to start though) but there is a
VERY
distinct pinging noise in the engine.

Friends tell me that's the sound of the lifters, and that even though the
sound is concerning to me, no harm is being done to the engine. When all the
bad gas runs it's course through the engine, everything should return to
normal.

When I first put the bad gas in the truck, it was about half full of clean
gas.
I then filled it up with additional clean gas with the intent of diluting
the bad gas. I also added a bottle of fuel injector cleaner, and a bottle of
"fuel preservative". At this writing, that tank was down to about 3 gallons
remaining and I just filled it up again with 23 gallons of Chevron Supreme.

Still making the pinging noise.

Can anybody here help me with explaining what might be going on with my
engine, and am I ruining it by continuing to drive it like this?

Thanks in advance for any help...

Mike
Tucson, AZ