Should I apply for a re-entry permit while transitioning from an ED Visa to a Thailand Elite Visa?

Hello, I am on a re-entry permit / extension of stay on an ED Visa, expiring December 27. I am traveling out of Thailand November 28, returning December 5. I have been approved for a Thailand Elite Visa, and have scheduled my appointment with them to affix the elite visa in my passport, at the DMK airport, upon my return to Thailand on December 5.

I have been advised by the Thailand Elite people that I do not need to apply for another re-entry permit before leaving, as I will be entering Thailand on the new visa, not the old ED visa.

First question: is that good advice, or should I request a re-entry permit anyway?

Second question: Should I request a letter from my school, and visit Immigration to cancel my ED visa before I leave Thailand, or can I cancel that visa upon arriving back in Thailand at the airport? If it matters, I will be continuing to study with the school upon returning, just on the Elite visa, not ED visa.

Thanks for any advice!