1)... Yes, the Trident's will fit with the Hyper 212. On X58 motherboards, you typically don't use the slot closest to the CPU, unless running 6 sticks.
2) Solid build overall, specially since you got the i7-940 for cheap
3) I would go with two EVGA GTX 460 Superclocked EE over on GTX 480. In Tom's latest review, it shows the GTX 460 in SLI is more powerful than a single GTX 480 at less money.
4) What is your PSU? You don't want to skimp on the PSU in a build like this.