Dealer ripped you off. They knew HG was bad. Get a lawyer.

Dealer surely erased all the CELs.

The engine is probably full of blue devil.

I got a 2005 4runner V6 with 150,000 miles and no HG issues .. ... yet!
My 4runner is in the Bahamas and never sees over 60 mph - except rarely.
Island has no Superhighways!

Gaber6 has good advice IMO.

BTW... I just checked my overflow canister and I check it often after reading about the HG issues here.

Coolant level has held steady - right at the same line on the overflow canister for the last three months. Hasn't dropped even a 1/4 inch.

Just wondering Inglysh, how many miles you gots on your 4runner?

In the meantime, I'd try those HG sealers (don't ask me which one - BD looks like the best) and watch the coolant level twice weekly.

Good luck!