HDV Format/Grading issues

Hi everyone, my first post here.

I've read around this issue a lot, and I've understood a fair bit, but the details of this still baffle me slightly.

We shot a music video using Canon A1, and captured as HDV 1080 50i (I wasn't aware at the time of Pro-Res speriority).
It has all been edited in HDV, uncompressed, and has a lot of scaling, time remapping, Twixtor etc etc.

Now, as is always the way, I have just found out Pro-Res is a superior format, and also a lot better for grading. Should I re-compress the whole timeline to pro-res? What is the best way to do this, bear in mind there is a LOT of time remapping etc, given the music video format.

How does this work with sequences etc in FCP?

Finally, the project size is something like 1920x1440, none of my scaling (applied to make camera-work more dynamic) goes about 140%, which is obviously quite a lot, but there we are. What are the best settings for re-compression given this?

Thanks a lot in advance, sorry my first issue is so involved, I really hope someone here can help...