Thread lock should only be used on screws that thread into metal, not plastic. As far as the how tight is too tight? Pay attention when you tightening screws down, when the head of the screw is all the way against the material (no threads showing) give the screw another 1/4 to 1/2 a turn and that should be good. The best advice for building a new kit is to slow down and take your time, if you need something, don't try and make something else work. Get what you need. Taking your time and doing things right will assure that your first trip to the track is not spent in the pits fixing a bunch of stuff and out on the track looking for parts that fell off your car, rather it will be spent out on the track enjoying the fruits of your labor. Good luck, have fun, and remember it's just a toy car.