Or the OP can just drop it in and check it out. If it doesn't boot, then take it out. If performance is slower, then take it out. Ram is really easy to install.
There are always ways to recover data from hard drives that have been wiped. It really depends on how much money and patience you have. If you are seriously worried, I would do what Ritorix mentioned and use a eraser/shredder type program that overwrites the sectors. That should be enough to...