File -> Open video file -> Streams -> Demux -> ("Name of Video") with .ac3 extension.
I'd encode video elementary stream only. And unless you want to wait a long time, use CQ, kinda like one-pass VBR, except file size is somewhat unpredictable. Quality is quite good. For that movie length, I'd use CQ 65 or thereabouts, depends somewhat on the particular movie.
When you have your elementary streams, use TMPGEnc's MPEG Tools to mux (multiplex) them together. That way you can check audio sync before you author the DVD.
And for goodness sake, don't do an NTSC -> PAL conversion. If you're in PAL-land, your player and TV should handle it fine. If you insist on framerate conversion, it's easier and better, IMO, to do it as AVI. Look here:
[EDIT] Oops, you stated you want to keep 23.97 FR. Never mind.