I built the Moebius LoneStar back in 2011 (Good Lord! Was it really that long ago? Wow!), and I do not remember any major assembly issues. Although getting the interior into the cab, the getting that back wall on was a little tricky.
This build was completely box stock (except for the door decals), although Czech Truck Model (CTM) does offer some P/E parts for the interior, frame, etc. to make the model more accurate.