Updating is kinda tricky, cause you need to learn 2 things - 1st, the old content system - 2nd, the new content system. If you're making something from scratch you can skip the 1st part, but if you're trying to update old content you need to understand how it works so it's possible to translate it. And some old techniques (like emissive throughout track materials) should be scrapped and done differently, so you need to learn about that too.
You can learn a lot just by comparing the Murcielago from (say) 0.6.5 and 0.8.20. The material names are probably 95% the same, maybe 100%, and they mostly work correctly now. For earlier 0.8.x versions I wouldn't recommend using the Murci to learn from cause it's not all Cg and has some oddities (the wheels reflect their own texture for example)
Once you've seen the general equivalences (what's a shiny body texture, what's used on tires, etc.) you can translate that to other cars fairly easily. Car and track shaders are far easier to write with cg, which is a plus to the new system, but you need to know which ones to use and set them up correctly to start with.
The new system enforces a lot of uniformity that the old one didn't, though - there's no more blendfunc=one_minus_src_alpha to compensate for inverted alpha channels when mixing layers. So you may have to go to the textures and edit them to make sense (100% = opaque, 0% = transparent) This applies to the Murcielago's window texture for example, which is inverted only in some parts for some reason.
In my opinion it's never too early to start learning the cg system. The more comfortable you are with it, the better you can make suggestions so Ruud can tweak it to work for the content creators and give the best possible experience in the next final version. Of course, don't expect any content you work on now to stay perfect - but it'll be easier to update if it's already got cg shaders. I've been keeping a couple of my cars (Aronde and RX-7) up to date with every new cg enabled version, and most of the time it's just a matter of reading over the version notes and implementing whatever changes were made. If you understand the Cg system doing these things is fairly easy.
I expect when the final is out, some guides will be made on setting up the basic shaders (matte, paint gloss, glass, etc.) so that anyone can just copy/paste them, insert their own texture+material name, and be done.