Technically, you should also have an "Install 3.0" diskette with your A1200. The disk contained the tools needed to prep a new or non-Amiga formatted drive. This diskette came standard with the A1200HD computer, but was NOT included in the early A1200 base models.
I know, because I bought a new A1200 that had a 160MB Quantum that my dealer installed, and he had to give me a copied A1200 install diskette, as the A1200 didn't ship from C= with the 3.0 Install diskette. ;-)
But, if your hard disk is already partitioned, you don't need the install disk, anyhow, and the procedures listed above are fine. The only tool of use you are missing is the "HDToolBox", and I think it's available free from some places, now, anyhow.