How to repalce charging port?

The charge port on nearly all iPads is a job that will need soldering know how to complete. If you have the gear and know how for that it's a fairly straight forward repair.

You'll need to follow the Logic Board replacement guide to get the board out. All the solder points for the charge port assembly are on the back of the board, underneath a sticker.

If you are not a skilled solderer, I might leave this one to the pros, but any good shop with a board repair tech on staff should be able to handle this.