So I got interested about making a sub for myself

I'd be happy enough with a square block which can shoot and as I'm not very good with any program that I could use for making textures so I guess it'll be that
Anyway, in case I manage to got a model done how can I add it in the game? So is there any tutorials for that or is anyone willing to teach me a bit..? Also does it require some program? I have S3D.
Thanks in advance and happy & productive hunting
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EDIT: I went to test my skills in modeling.. Apparently Google SketchUp isn't as simple as it looks xD Well, I made something between a brick and an aircraft carrier.. And yea, don't tell me now that every part of the ship has to be done separately and later added to it..?
Took a rough print screen and here is what I've got done:
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Elektroniikka-Asentaja = Electronics Assembler. In finnish, Just in case someone wants to know..
New rig for noisy running:
Desktop w/ Asus P5QC motherboard, Intel Core 2 Duo 2,94 GHz processor, ATI Radeon HD 4800 series graphics, 4 GB DDR3 Ram and 1297 GB hard drive memory
There is a good possibility that the above post was written with a phone so please forgive the typos