What a whirlwind of emotions and it was truly my first solo trip! 
I met up w friends while there and am so thankful for the first to show me how to use Naver Map and Kakao Metro on D1 because after that I truly was on my own!
I landed in Seoul and spent the weekend there and then took the KTX to Busan. In Busan I used the buses to get around and then came back to Seoul via train too but did not know it was not a KTX, I ended up on the ITX-SAEMAUL which was fine as it allowed me to nap after a few days of GO GO GO.  I bought these on the ktx app.
Attached is a SS of the apps I used.  I might have paid more but I wanted to have a working phone immediately upon landing so bought an eSIM card. 
I will go into details later, I'll edit my post but still on a high that I took myself out and don't regret it.  I've been living in Europe for 7 years and though different it was a great