I think people should learn on their own, you can be proud of what you've done that way. If you get help then your not really getting the satifaction of what modding is about. In my honest opinion.
You have to really be interesting in modding to actually do it, for example ive always wanted to mod TDU as soon it was released. So when I saw Djeys tools and other things I was excited for it and now im still going. I suggest never do modding if you just want 1 car that maybe someone wouldn't do or something cause your wasting time and money.
Though always there is the few people who want to do modding either for just a modder badge or cause their request isn't being done. So think about what you really want to do before you just go ahead and pay 60USD for zmodeler and see if you can do it. Otherwise your just wasting your time and also money.
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Just like 'Mr Spongie' said, you can download the car demo pack and download the demo zmodeler and you can do a mod on the alfa GT. That's how I learned and then over years I got better.