Absolutely! 35 mins is way too short especially since you're upgrading. And call UA as soon as you wake up (assuming it's inside 3 hours before flight time) and have them do a confirmed same day change for you assuming there's space on the flight.

You didn't ask and I'm sure you already know this..but you should also inform LH over the phone the day before that you intend to upgrade so they can be sure they cater enough meals in F.