I've done Trail Peak four times, and it's a great hike - what hike from Cottonwood isn't?!
Depending upon whether you take trails, or cut crosscountry, it ranges from 5+ to 6+ miles.
However - for elevation gain - it's a bit over 1,600' according to the GPS logs from my Garmin. Steve C. - was your 600' a typo?
I have a different approach to conditioning/acclimation before a Whitney (or any other 14er attempt). Personally, I may go for a short walk the day before of a mile or two, with maybe 100 or 200' gain/loss. More than that and I jeopardize my chances the following day. YMMV.
