Dave,
You have done a wonderful job on the engine, especially hand painted. I'm not as much of a car guy as the guys who haunt this forum, but to me, a model is a model. There are just different techniques and stages for planes, armor, ships and autos.
As far as painting, most members will prime so the paint will adhere to the plastice better. For a high gloss shine for autos, several light coats are required with sanding between coats. Most guys will use a very light grade paper, usually in the 1000's +, followed up with a final coat of gloss, but it's preference. You will find that you will find what works for you and tweak it as you go along, gain experience and tools.
Also, to dress up items like engines, I will use items like wire stands, for spark plug wires, tubes and hoses, and paint them accordingly.
You will begin to see things in miniature. A tulle lace at Walmart or the dollar store can become a screen, chicken wire, net, etc. Wire strands and wire insulation become hoses, conduits, cables, etc. Solder is easily bendable and can be made into a variety of items.
Most of the work you see and are impressed by, are built by members who have been building for many, many years. I myself have been building since I was 5 and am now 54, with a 15 year hiatus in between.
As long as you are enjoying yourself and like your results, that's all that matters, this is supposed to be an relaxing hobby after all.
Just stay intrested, do the best you can, and always try to improve, and you will be surprised just how soon you will be building models that rival those that impress you now. It's such a kick to work on something, stop, pull back, take a break and look at it again later and say WOW, I made that?
Happy modeling, and hope to see more of your work
Steve