I know there was a lot of general speculating about gearing in the other thread but that bike is good to go, for what you want to do, as is. I wouldn't over think it. It is already far better than several of the bikes I have done tours with in the past.
As Djb mentioned. Those things aren't replacements as much as having a good mechanic give it a going over, similar to someone taking a car in for a check over before a long motor trip. I think old people still do that with their Buicks
Generally, the things people upgrade / change / personalize are contact points: saddle, pedals, bar tape. And good tires.
There are many threads about saddles, it's a topic with lots of opinions.
For pedals, the big decision will be platform or clipless. Bartape is again, one of those "everyone has their own idea" things. Same with tires, though there are a couple of common favorites.
Beyond that you will have to choose panniers. Ortlieb seems to be the benchmark brand for many. Then tents sleeping bags, cook stoves etc... lots of fun!
One thing that would help in making suggestions is your budget expectations or desired quality level. Lots of people get carried away with theoretical dream builds but reality dictates how much one actually intends to spend on stuff. You could retrofit a lot of parts on your bike but at some point you would have been better off buying a more expensive model.