For something like this, You will want to start out, make a low poly model, get the basic form and shapes down. get the correct size and proportions. once you do that and are satisfied with the low poly part, Save it then Save it again as a new file, call the first one, low, and the second mid, or something like that.

Add detail as necessary to the second file, until you are satisfied with that one also. repeat as necessary for the further detailed versions.

As far as the high poly model. You'll want to use a mixture of Bevels and smooth poly operation. For a high detailed poly model, both are a must, Unless you want to suffer from a fake cg looking render with impossibly hard edges.

Look at hard surface cornering on real world objects and you will see that there is no such thing as a perfectly cornered edge, even the best milled edges have beveling to them.

As far as what to use bevel on and what not to. That is something you just learn with experience.

You have some geometry that will never be seen at a truly close distance, and isn't part of the main superstructure of the model, then Bevel it, there is no reason to waste the poly's on a smooth. and vice versa

you also want to decide what detail you ant to model in and what you want to texture in, or bump in with a bump map. you also have the option of creating a displacement map as well. Bolts and Rivets, unless you plan on going a pov shot from some poor guy getting decked and landing eyeball first on a rivet or bolt, there is no reason to really model one in, unless you just want to. at-least on a model that's this size anyway.

Basically, its a balancing act, you will have to find the proper balance, between poly's detail and textures to pull off the effect you want to achieve.

Hope this helps
G-man