If you put a generic hard disk in, you must have the mounting plate and connector cable also.
The factory drive comes with a large number of midi files. Nothing you can't get elsewhere though. I thought it was also supposed to have the MS styles, but the one I just installed for HankB didn't have any styles on board. No problem, they are readily available.
There are about 22 screws to take out. After that the installation is quite easy.
I would recommend getting the expansion memory, but it isn't essential unless you use a lot of user styles.
There is no overall e.q. or compression, other than the facility to boost or cut the bass. In fairness, it really isn't necessary because the Ketrons sound good when you turn them on.
Hope this helps.
DonM