Dont't doubt your abilities if you are well prepared. As long as you have done the proper research on GTPs (like reading The More Complete Chondro, or sifting through husbandry posts on several of the forums available ie: moreliaviridis.com, moreliapythons.com, here, etc) you shouldnt be too doubtful of yourself. I had never kept snakes, I had only kept Bearded Dragons, Leopard Geckos, and Argentine B&W Tegus, but I bought a baby GTP after the necessary research and preparation and honestly it was the best purchase I ever made. I am absolutely addicted to these snakes now. The horror stories you have heard about come from people who have dealt with fresh imported chondros. As long as you deal with a reputable breeder to get your baby then you should recieve a healthy, feeding snake that is backed up with years of experience from your breeder and minus all of the ailments that imports so often suffer from. I have learned in the past two years of GTP keeping that if I cant talk to someone who bred these snakes then more than likely it isnt captive bred...400$ seems slightly close to the line that seperates captive bred from imported babies. There are several nice babies in the classifieds here currently. So, to avoid the horror stories you heard about make sure you go with a baby that has a breeders name at the bottom of the ad. Best Wishes to your future in chondro keeping.
Warning: Once you get one...you will be contemplating ways to get more and more.