Modifying existing available 3D models for printing... (Software question)

[Kenworth]

There are a number of sites online with existing 3D models available for free or for sale, and as far as vehicles go, there are seldom print-ready files among the choices. Supposing I'd buy from Humster 3D (a good example, they have vehicles I'd like to do), what would I need to do to the type of file they'd deliver to make it print ready? I would be making it in a Makerbot Replicator 2 in a size that would fit the printer bed, and if I'd go a little bigger I can always cut the shape in half with Netfab. I don't care about realistic photos on the computer with reflection and colors, I just want to be able to print an accurate version of the vehicle.

I'm guessing I'd buy it in the .obj format, what would the ideal software be to make the existing model print-ready? They offer it as a service, but it's expensive (the file as it is on their site is only $100 or so, which is OK, but $500 each file to make it a printable shape will rack up some serious expense, especially if I'd want to do it over and over again (which I do) and I'd like to learn. My problem is I don't know exactly what it is that I want/need to do (specifically what it's called, so I can Google it or learn it on Lynda.com).

I've been playing with Meshmixer, and have Maya, 3DsMax, and even Solidworks... and am not against buying something like Zbrush. If I could get a few people's suggested approach to this problem, I'd greatly appreciate it. Whatever software, or whatever approach, let me know how you'd go about it and with what software, so I can get pointed in the right direction, or maybe I'm approaching it all wrong and should start with something different.


Thank you!

Here's a screengrab of some of the vehicle choices, and the formats you can choose upon checkout.