Yeah, TMPGEnc is as straight-forward as it comes for converting AVI to MPG2, just make sure you output as separate MPG video/MPG audio streams (the setting is ES Video+Audio). The high-end apps take each stream and sync them together during burning. Make sure to fix the GOP headers of your resulting MPG video stream before you burn (to guard against audio being out of sync with video). MPG audio takes less space on your DVD than LPCM, but LPCM is the better stream of the two.
Cucusoft is good for conversion, but doesn't split the streams. Any resulting video still needs to be split into audio and video streams.
There are numerous, lesser-known converters available, but all come with some type of headache like freezing, limitations, embedded spyware, etc. Stay with high-end stuff, even if you have to pay for them, and you won't run into headaches.
TMPGEnc's DVD authoring app is pretty good. I use DVD-Lab Pro because it offers extreme ease of use with very high-end options/tools. I also use DVD Menu Studio in combination with DVD-Lab Pro to very quickly make menus that blow away anything I've seen any other authoring apps spit out.
Check out this page -->
http://www.videohelp.com/tools
It's pretty much a one-stop-shop for all you'll need and even some extras you never thought of. Almost every app offered comes with step-by-step user guides. Aside from this particular page, the entire site is essential to getting started with making DVD's.
