Does the audio on the timeline have to be 48k?
I need to bring in a soundtrack from a CD. Would that be a 48k audio or would I have to convert the soundtrack to 48k?
I am thinking the CD audio might be 44.k..I will need to lip sync some of the video to the audio ..
Audio from a CD will definitely be 44.1kHz. You will need to resample that to 48k if you want to put it to DVD, but this can be done at any time during the project, even during authoring. I would do it early, though. No great reason, just my habit.
Vegas can handle just about any format you throw at it. Leave it as 44.1KHz when you put it on the timeline and it will work fine. Vegas will automatically convert if necessary when rendering without you having to do anything at all.