how do I replace the high side port?

Yes, this is easy to replace, I assume all of the refrigerant has leaked out correct? Here is how the job is done and I have included a video to help with the A/C vacuum down and recharge.

https://www.youtube.com/watch?v=4EqdrBVb0sY


Check out the images (below). Let us know if you need anything else.

the parts in the middle do it just screw out? I tried a 5/8 wrench but my wrench want to slip. this is valve core wrench I'm using trying to remove the core but nothing come out.

Yes, it wont it is made as all one piece I would try vise grips to get the valve assembly out.