Hello!

I used to work a few years on computer game models ... there are few things to think about, you won´t be used to from modeling with high-end-maya ...
i modelled in Milkshape that time (veery simply, $20 Program) ... but its good for this type of work.
Because you need to have control over every single polygon, for example: if you have wheels, you won´t use the tops and bottoms of the cylinder, but use rectangular surfaces (2 polygons) with transparency map ... if you model that way all the time (lots of transparency maps) you can save a-lotta-polygons ...
i modelled trains (https://www.bluesky-interactive.com/S...T2/final11.jpg) and they had as well about 3k polygons, with insides ...
hope i was able to help you
ulrich