With your cost limits (I understand those), I would recommend Final Cut Express. It has the same interface as FCP but can only work with the DV format. That should be fine for you learning how to edit. FCE is really a great bargain. It's how I learned the Final Cut interface after outgrowing iMovie, before I ended up shelling out the $$$ for FCP. Try getting an educational version if possible ($$$ savings). I use Apple's pro apps now, but really started my understanding of true editing with FCE.
My suggested workflow (inexpensive or free):
MacTheRipper: Rip VOB from DVD (one big muxed file that contains audio and video)
MPEG Streamclip: Convert ripped VOB to DV format
Final Cut Express: Load converted DV files, edit away
iDVD or whatever else you like: Authoring/Burning
Good luck. At full retail, that's around $300. That's a nice machine you've got and it will do great with what you're wanting to do. And, I'm still working on those scans. I swear...
