Does this picture help? I've bought one of these off of eBay from a used restaurant supply house. It grinds nice and even for espresso and has just a small amount of fines doing course grinds. Since I usually only grind enough for a couple of doubles at a time, the doser is more hassle than it's worth. I usually just dose into a small bowl and use a pastry brush to clean it out each time. A doserless mod would be nice, but I haven't seen one.
I'm not sure what the spring is in your second picture, but the pin is for the step adjustment for the grind settings. The bottom of the adjustment collar has holes that the pin goes into to keep it in position. There's a hole it goes into in the top of the case on the upper left side just under the edge of the collar.
Looking at your top picture, it looks like you need at least the doser handle and the brass bin that keeps the cam from turning the wrong way. It goes in where that spring is sticking out at 2:30 in the top picture. It's hard to tell what other parts you may need inside the dosing chamber from your picture.
I'd be happy to help out if you have more questions. Just let me know.
http://www.espressoparts.com/category/03.03.rossi.rossidoser/