The pictured engine is obviously an engine removed from one of the many many that cox provided for various vehicles along their toy road.
It looks like the fuel enters from an outside tank through the black fuel line. It looks like the long stem on top is a form of needle valve.
To change glow heads, notice the small indention on the silver glow head (one each side). That is for using a cox engine tool to unscrew the glow head. Without such tool, I have found that a nice pair of needle nose pliers, properly applied, can perform such task. There should be a copper gasket under the head. Use care to save it.

A tip that is seldom advertised or spoken of, is that small engines like a lot of cooling oil. Most users speak of the requirement for high nitro. That is incorrect as far as the "NEED". The standard cox .049 is very happy with a 10% nitro, and at least 20% castor oil. I have 3 that I have been flying with, kids using my original design models ranging from 18" w/s to 24" w/s, two being almost 20 years old and one only 8 years old. They start easily with the spring starters, are easy to needle using the stated fuel (old ducted fan engine fuel) and run very well, certainly well enough for sport use.