2011 Prius 164 K Replace the Head Gasket or Engine (w/ Gen 3 or Gen 4)?

new to the form, been reading it for years. Appreciate all the advise.

My 3rd Prius; 2011with 164 k, needs a Head Gasket... or a new Engine. Do I do the Head Gasket and EGR or try to find a JDM Gen 3 or swap with a Gen 4 2016/17?

Current Engine. No oil Leak, used some coolant the couple days right before I stopped driving it, EGR was causing jitters at start-up. Temp warning light came on for less than a minute, then went away and never came back on. Changed the Plugs recently and nothing stood out as really followed/dirty build up. Took it to Toyota for the first appointment I could get. Now it's at my Mechanic waiting on my decision.

A Used low Gen 3 Engine may have probable Head Gasket issues down the road. Every thing else seems fine with the current engine although I do not know about the rings?

I have a good Mechanic.

Seems the difference in the two options is perhaps $300-500

Thoughts?