I only have half an hour to an hour to train most weekdays, can I get anything out of that?
Yes, but try to fit your priority workout in on the weekend. Endurance sessions of half an hour should be done primarily in level 2 and should include a few bursts of speed. Strength can take as little as 10 minutes a morning if you can wake up just 10 minutes earlier. Warm up for intervals can take as little as10 minutes, the workout 35 minutes and the warm down 15 minutes.
One more hammer session?
The big race is coming and I think I can fit in one more tough interval session and maybe another long ski.
Don't. If you are feeling good, you want to stay that way, if you aren't feeling great, at this point you won't get that way by training.
Final preparation: Take it easy the week and especially the few days before the event. It is quite possible that many are starting the race with the tank a bit low. Skiing long or medium hard to hard depletes your glycogen stores. You cannot get in good shape the week before your race. The time for that is in the months before, right before the race is time to tune up with some easy skiing, some short (!) bursts of speed or a little (!) race pace work, aimed at feeling good, rested and excited not at getting in shape. The workouts should not break down the body.
When I can, I follow some variation on this commonly used routine:
Sun: long very slow distance.
Tues: (off, if tired) otherwise speed or very easy.
Wed: very easy distance.
Friday: easy with speed.
Sat: Big Race. Pacing: Start at your own pace. (You know who you are.) If you go anarobic before you are warmed up you are more likely to bonk.