A couple of bags of top soil from the garden center don't cost much if you want a little better soil for the big pot.
It's up to you. What ever you put in the big pot water it the night before. Dig a hole the size you need pop the plant out of the little pot and drop it in the hole, add a little soil to fill in the gaps. Press down a bit and water it in well. Super easy to do.
I do top pretty young. But your plant needs transplanting now. Then give it a week. Or watch a video on low stress training. Once she is happy in her new home Pull the top over and tie it down. Point the top to the North so the sun hits the plant stalk. She will take care of the rest.
I understand about over watering. If you water well then let her dry out between watering she will be super happy. Just don't water it all the time and your good. Guys get into trouble watering the plant every day or 2 even 3 times a day.