I don't resize usually, I try to export out of Final Cut at the frame size I want to use. (Though I may resize for a dial-up version of my video.) It's easy to do by choosing a custom frame size and typing in the size (640x480, 768x432, or what have you.)
I believe that M4V uses the H.264 codec. You could probably also export out with Quicktime MOV with the H.264 codec, or MP4 with the H.264 codec, and they would probably look equally sharp. (Though H.264 MOV are not the favorite downloadable file type, but streaming video sites like Imeem will accept them with no problem. And anyone with VLC Player or Quicktime can play H.264 MOV.) Many amv people here favor H.264 MP4 files.
It may not be desirable to export out as uncompressed, only to convert to a different file type (like XviD AVI or DivX) using a third-party encoder (like ffmpegX) but a lot of the Windows-based amv members do this all the time, so it's standard procedure around here.
In any case, I think you did well to get Premiere Pro, since you'll be able to upgrade it. I really like Premiere (the little bit I've used it), so have fun learning how to use it!
There are a lot of Premiere users here, so you'll be in good company.