Yes. Any external hard drives will work with final cut pro.
However, there are a couple things.
Your machine does not support FireWire 800. Your machine also doesn't support other things Final Cut Pro 4 demands. The minimum requirements are found here: http://www.apple.com/finalcutpro/specs.html
Instead of spending 1000 on Final Cut Pro 4, I'd recomend buying a newer mac first