2011 outback 2.5i 125K with head gasket issue. Worth to fix it?

My car started having over heating issue.
I took it to a shop and replaced radiator.
A week later, it was overheated again then replaced water pump and then
thermostat. A mechanic told me I might have a head gasket issue but they
can't tell. Ran two tests, hydrocarbon and block test, failed once and passed
twice.  I was told there is no external leak so I might not run into another
problem. but no guarantee about that.  

Took my car to the other place for the second opinion.
The second place told me that they see internal leak through #1 cylinder and
minor leak from #3 cylinder that I need to get my head gasket repaired.

I already spend $1300 on my car and might need to spend 1700 for the
gasket repair. I know nothing about car and need an advice.
Is it worth of money to put another 1700 for the repair or get a new car.
I would like to keep my current one if repairing the gasket can guarantee my
car can run another 50 to 70,000 miles without any additional major repair.

I need Advice!!!
I appreciate for your help