So I have a couple of rolls of Kodak Ektachrome P1600x (EPH), and I'm still slightly confused as to the following:

If I re-spool it into ISO400 cartridges (my camera doesn't have DX override -might get a better body soon) and use it as such, do I just tell the lab to process it as regular ISO 400 with no pushing or pulling?

What I can infer from the cartridge is that if I expose it as P1600, I just mark it as P2-1600 and the lab will know what to do with it and they'll just charge me the extra for pushing it (not sure if all labs charge extra).

I got it mainly for experimentation, however, over the course of the last year and a half I had less and less time to play with film, and I actually sold most of the P1600 I got, since it was just taking up space in my freezer, but kept a few rolls.