Regarding the sleeping, I don't believe that there's any sense in "practicing bleeding" I went to Quantico from CA twice and adapted quickly to the approximate 5-5.5 hours of sleep that we averaged a night. The Sgt Instructors and your billet holders will keep you with a high stress level the entire time and your body will adapt quickly. I don't know if Navy OCS is different, but after taps, we always had something to do before really getting sleep, whether it be laundry, squaring away your trash, shining your boots, studying, writing essays, or meeting with your squad. I would say proficience in being able to get that kind of stuff done quickly will get you more shut eye.
As far as what to expect from OCS, I don't think anything's a big secret. Everyone will have different tribulations at OCS, so I would recommend picking the brains of those who have gone through. It' no secret that the SIs will have a sea bag drag the first day (so pack everything in zip-loc bags), humps are tough on your feet (so bring moleskin and anti-chafing shorts), or bring a borken-in pair of the MARPAT boots.
OCS (for Marines anyway) is a screening process and a right of passage. I've heard of many DIs and former SGT instructors going through (and you can bet they know everything coming at them). The best feeling of OCS is definately completion and graduation, but it's mostly from the feeling that you got through with your fellow candidates from your platoon and company. It's what you can bring to the table to lead other candidates, not be the one dragging ass and waiting to see what's going to happen.
Make it happen,
-Itoh