I upgraded the internal drive on a few days ago with the 500GB Western Digital WD5000AAKB. I didn't have a security torx T10, but I own my 8300HD. The security pin inside the three bolts are very thin and I simply broke them off with a small screwdriver, effectively converting the bolts to use the standard T10 torx.
As for the drive, quiet, everything works great. Drives spins down when power is off.
I debated so long about internal vs. external, plus there wasn't a 100% confirmation on the net that a 500GB internal would work until this thread became active again (thanks!). Internal was the way to go for me. It's like it was before, just triple the space.
Took less than 10 minutes, formatted right away and was ready to use.