To convert PAL to NTSC is very easy, but as Shadoe said, you will end up with a very jerky result. PAL is 25 frames per sec, while NTSC is almost 30 frames per sec. Like where does the extra 5 frames every second come from? not thin air. TMPGEnc at the end of every second, or 25 frames, it just repeats the last frame another 5 times to fill in the space. End result, an unwatchable jerky movie.
If you realy want to do it, just follow the Tutorial but in TMPGEnc select NTSC template and set screen to 16:9 NTSC. Any further problems, sorry, I cant help you with them.