Yeah, the course is open whenever you want to run it. EXCEPT during certain times during hunting season (sometime around now). A bunch of the LT's would get together on the weekends and run it as a group. You have to run it with either one or two other people (safety).
Gear: I think was boots, M-16, flik/flak, kevlar, large pack, extra pair of cammies, full canteens and camelbak, I don't recall anything else being required in the pack. It wasn't much in the pack. You're allowed to sling your rifle as you wish too. Some people would strap it across the top of their pack, but one obstacle makes you climb through a window --- the rifle would hang up and they would have to take their pack off.
Splendid is right --- walk up all hills (quickly) and run your butt off going down all the hills. Jog on all flat terrain (there isn't much). I didn't train for it at all and did really well with this technique. The staff will tell you to do it this way too. It's pretty motivating. It rained on us (lightly) when we ran it and it just motivated me even more.
I think the first time you run it, you'll run as a squad (just to be introduced to the course). Then you'll run it a second time (time doesn't count). Then you'll run it a third time for real. But, if you don't pass the second time (the not graded one), they'll put you on remedial PT (evening and weekend PT sessions). We had an LT in our company that stayed in Quantico until August until she passed. She got Mono around the same time we ran it so she wasn't able to. Then once she got over being sick it took her a couple months to get back into shape to complete it in time. Moral of this story: if you pass it the second time (the one that doesn't count) and can't run the real one for some reason -- they may use your time from the earlier one and allow you to graduate. It'll be a consideration at least amongst your company staff.
Don't sweat it.