is he ps2 HDD compatiable with the ps3? would it be able to read my saves? or would the drive have to be wiped before it could be used?
Your PS2 hard drive isn't compatible with other PS2s, let alone the PS3. Both the PS2 and PS3 (annoyingly) lock hard drives to consoles, probably as some bullshit security measure that just makes everyone else miserable when their systems fail and they can only depend on an incomplete backup feature.
Ok, now that I have that out of my system the PS3 also uses a different form factor and connection. The PS2 hard drives were modified IDE desktop as I understand it, while the PS3 uses standard SATA laptop drives. This also means however that for something like 80 or 90 bucks you can get a 500 gig hard drive off of Newegg and never have to worry about memory again.