Chico,
this issue has been discussed at lenght on this Forum about the Tyros; Scott and Terry know everything about it.
Basically, every hard disk for a laptop computer will do; I have installed an IBM 20 GB, even if the 9000 pro can read only 8 Gb (but today is really difficult to find HD smaller than 20 Gb).
Installing the hard disk is really a piece of cake; you will even find the screws already in place inside the cover. The whole process takes about 15 minutes; the most annoying part is turning the keyboard upside down (I did it on my bed, to be sure that I wouldn't have damaged anything in the upper part).
Good luck.