It'll probably run ok with it being a dual processor. I think I've tested Final Cut 5 on a single 1.25 G4 Mini and it ran ok. It would be better trying to get an Intel machine but there's not really an upgrade path for you as a Mini has a slow HD and isn't upgradable. The lowest Mac Pro is fairly expensive if it's for occasional work.
For learning on, I'd say it'll be fine. Final Cut hasn't really gotten slower so it should run fairly well.
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For learning on, I'd say it'll be fine. Final Cut hasn't really gotten slower so it should run fairly well.