Head Gasket/replacement...questions about engine health from the overheating.

[Thomasaquinas]

Hello,
I have a 2007 Toyota Yaris which has about 150,000 miles. I love this car and it
overheated on the highway. The car shutdown which freaked me out. I had it towed back to my yard and replaced the water pump as well as the thermostat. Afterwards, I started the engine and white smoke started coming out which is indicative of a head gasket failure. I ordered a block tester and will do the test myself tomorrow.

I have a quick question. I don't have the money to replace the engine totally, but I want to do that in the near future. My question is if I did a head gasket replacement myself, how likely is that i can get this car driving at least locally? I guess I am afraid that their is damage to the head or block from the overheating. Is my only choice to replace the head gasket to find out if the engine is damaged?

I love this car and I will not dump it. I just wanted to some input regarding how to proceed and how to get this car functioning again.

I am including a picture of under the hood where it looks like there may be some soot from the overheating.

Is their any other way for me to check the engine block and head for damage besides during the actual replacement of the head gasket?