The topic here is IMPEACHMENT, not the 25th Amendment.
Key facts:
Trump will not be removed using the 25th Amendment.
The odds of that happening to Pence, were he to become POTUS, are so remote that even bringing it up just makes you a subject of derision.
No...the TOPIC is as follows in your words: “Whoever is President can appoint a new VPand the Senate can confirm the appointment”
I suggest you read the Section 2 of Amendment XXV. The House of Representatives is also involved in the process you describe.