It's certainly possible for you to win. You've got a defense with great athletes and a great coach telling them what to do. Oregon will be fielding an inexperienced QB, and will likely be coming in as the favorites having to deal with the hype. And certainly there is no place like Neyland in the Pac besides our humble abode.
I caution you against believing that Oregon will struggle with the heat and humidity. The fact that the game is at night will make that less of a factor, as previously stated here, but beyond that Oregon is a team that takes a great deal of pride in being one of the best conditioned teams in all of CFB. This is a critical point of focus for a program that has firmly established its identity has high-flying and breakneck in terms of tempo. In point of fact I would say that upwards of 80% of our opponents end up gassed midway through the third quarter because of the ridiculous pace the offense operates at. (And I would say last year we were actually a little slower than we had been in Bellotti's last year as HC.) Also one of the features of the indoor facility is fancy climate control, so the players will at least have a week to acclimate to what they might face.
The key here is that the QB will have to execute for any of this to matter. Masoli had a terrible time throwing in the Rose Bowl - and not only when he was under intense pressure from that impressive Buckeye pass-rush. Similarly in the Boise game he never got going. But if Costa or Thomas manages to come out and fight through your crowd, Oregon has the pieces to dominate the game.
It will be a really tough way to have a new (and while Costa is a 5th year who knows the offense like the back of his hand, I would still call him new) QB try to find his legs, that's for sure.
Lastly, by my count only 5 times over the past 3 seasons since Chip Kelly arrived have the Ducks failed to score more than 20 points. I would estimate that it will take at least that to win.