Hey there,

you are right, learning by projects is great and can be fun or frustration on the same side ! That looks like a good start although it seems already very detailed. Maybe you already have too much edgeloops here. You should go first very rough and keep your polycount quite low. Start creating the shape and its big sections first. Maybe the mainbody, wings, engine etc. You´ll get detailled enough later. If you start by a too dense mesh now, you´ll could get into trouble later, when its time to work out the actual details or you need to fix some bad areas then you have to work with a lot of vertices!

For your AO render!

Load and select Mental Ray. Open Hypershade and create a Surface Shader from the Maya Section and then in the Mental Ray Section under Textures also create the mib_amb_occlusion node.

Now you should have the two nodes in your work area on your hypershade. Now middlemousedrag the ambient occlusion node onto the surfaceshader and choose default. It should connect the occlusion node to the OutColor channel of the SShader. Thats it.
Apply it and render it. No need for Final Gather or something else!

For better quality you can go to the occlusion node and crank up the samples up to max of 64 which is definitely superb...a value of 24 to 32 should be fine aswell. In your rendersettings go to quality and change to Max Sample Level of 2 and a Min Sample Level of whether 0 or 1...