The eggs form soft inside her, by the time you can feel them through her skin, she should lay roughly within two weeks. Most females go off their food, then with search around the enclosure, I can pretty much pick within a day or two when they will lay, but it won't hurt to put a tub in early, she may do some test digging in the days before she lays the eggs. Make sure you feed her heaps of insects whist she is gravid as she will have the next lot of eggs on the way before she lays the first lot, they can lay multiple clutches in as little as 20 days apart from one mating if fed well and in good condition.
Heat cord length depends on the size of your enclosure, but you would not need a long one for an esky, and any decent probe thermo will do for beardies, though a dimming one would probably be the pick for a incubator.
