Welcome to EAB
Well, first of all here's the link to 'Big Book of Amiga Hardware
and secondly, I think you'll find it'll be a SCSI HDD, unless it has an IDE Controller card fitted, like an Apollo.
Installing workbench only requires you to boot from the Workbench HD Install disk. It should ask you to prepare your HDD (partitions and format etc...) then it'll ask for the rest of your workbench disks in sequence until finished (i.e. Extras, Locale, Fonts, Storage etc...)
I think maybe we better wait until you have recieved the A3000 so you can inform us whether it's using a standard SCSI HDD or an IDE HDD through a controller card.