It's really just another plastic kit like any other. Fill the seems as you normally would. I've never felt the need to pin the joints, however I would pin the feet. It will give you something solid to secure it to the painting base and later the display base.
On color, you have to take into consideration the effects of weathering and the fact that, because of the nature of mass production, one sample of a garment could be a completely different shade of a color than another, because the two were produced in different factories. So, as was explained in another topic, the helmet could be anywhere from dark gray or green, to a lime green or tan. Branch of service and theater of operations will vary the color as well. A basic rule of thumb for figures is to never paint the pants and the blouse the same exact tint. Lighten or darken one or the other to vary it and weather it accordingly.