I wouldn't bother with the cycling shorts. I would just use the same outfit through the whole thing. A sprint is short enough that the time in transition really counts and it would be fine to ride in your compression shorts.
As for making up for lost workouts. Don't bother, just act as if you hadn't missed a day at all.
Have fun at your race!!
Living life like there's no tomorrow.
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2007 Look Dura Ace
2010 Custom Tonic cross with discs, SRAM
2012 Moots YBB 2 x 10 Shimano XTR
2014 Soma B-Side SS