The upgrade is done, now I have 39Gb worth of music space (12Gb + 30Gb). IBM Travelstar added to an IBM Travelstar, no problems.
The hardest part was finding the screws and washers and having to buy 5 jumpers because they wouldn't sell me just one...
Luckily the sysadmin at work needed some as well so he bought them and "loaned" me one....