Size of model: Depends, you need a consistant scale, for example one modeling unit can represent any metric system, be it one inch, or one foot. If you do that correctly, you won't need to resize them in your projects.
If you want modeling references:
http://image.google.com
As for those other questions, I'm not sure, I'm not a DarkBASIC user anymore, and it's been 3 years since I last used it. As this is the 3D chat section (Modeling), you'll want to ask the questions regarding the programming parts in the appropiate section.
Hope that helps.
I'm not looking to join any amateur teams, nor do I take requests.