I don't have a specific code example for you, but I can outline the process you'll need to go through. Basically, there are two things you'll need to do: 1) resize the frames from 720x576 to 720x480 and 2) change the frame rate from 25fps to 29.97fps.
For resizing, you can either just use the ippResizeSqrPixel() function (resizing each field independently if the material is interlaced), but this will break the original pixel aspect ratio. Alternatively, you could crop the PAL frame down to NTSC, but then you lose some of the content. Or, you can scale the 720x576 to fit within a 720x480 frame by adding black bars on the sides.
The frame rate conversion can be a bit tricky, and depends on if the input is interlaced/progressive, and if you want the output interlaced/progressive. Do a search for 3:2 pulldown since you should find references on how to perform the conversion in a standard way. It basically involves repeating either fields (for interlaced) or frames (for progressive) at a regular interval. You'll have to do something a little different if you also want to convert interlaced material to progressive.
I don't know of a quick single call in IPP to help, but it does have all the tools you need. I hope that helps a bit, Peter