I don’t think it is impossible but maybe pretty unlikely. I am sure you can improve greatly on your time given how it was timed and all but in 1 month you won’t be able to make huge gains. P90x will get you fit but it is not going to improve your 100m unless you are very out of shape and possibly over weight which you are not. I wouldn’t recommend sprinting later in the day after doing P90x on same days. If you are all about continuing with P90x then maybe do that in between sprint days or something like that. The circuit style workouts in the morning are going to make you pretty tired for sprints which you don’t want. With regards to sprints, start off with a bunch of acceleration stuff and progress out slowly with distance. If your only goal is to run fast by January 6th then you might want to add slightly longer runs in there, but my guess is that is just a short term goal and you will continue training. You don’t want to blow through proper speed progressions. I would recommend you do your homework on here and see what other people are doing for training and maybe read a few articles. Keep your training simple since you are new to the sport. Try out a bunch of different events! Jumps, sprints…maybe even throws? Have fun with it…personally though, I recommend you do HJ because that’s my favorite.