There are problems involved with installing a drive that may be larger than the system BIOS. Western Digital and Seagate should have instructions and drivers for your PC to recognize the drive as a 3 TB drive. With drives becoming larger (in 1983 a 10MB drive cost hundreds of dollars) now, only the latest PCs will be able to squeeze every drop of space out of those large drives. The rest of us will have to either switch the BIOS if possible or buy a new system. As for an external dock, it should work, however it's quite possible without a driver, the drive will not format to 3 TB. The documentation that came with the drive should explain drive formatting.
Concerning the USB, it's the same as an external drive in a dock.