First time at Disneyland Paris - a single Sunday in June

[pindecisive]

So like the title says, I'm planning to finally visit Disneyland Paris (Disneyland Park) in June on a Sunday. Sadly the date isn't flexible and I'd be flying in for the day from LHR and taking the TGV (Train à Grande Vitesse) from CDG then flying back/taking the train back to London at the end of the day.

I've done this with DL and also done full days in other countries (flying in morning, flying out evening), but I'm curious if there's any tips anyone could share about TGV, Premier Access Ultimate, or what I should hit as a first timer.

Thanks in advance everyone!