I built the older version and had no particular problems. I wouldn't worry about aftermarket parts at this stage, as I don't think it needs any. You can decide as you go along. Just be prepared to do a lot of priming, painting, and sanding as this big beast will take a lot of it. Consider using large cans of spray paint such as Krylon as it will cost a fortune if you use the little bottles of Model Master or whatever paint.
As for decals, there aren't many, the ones that come in the box should be perfectly fine.